DOC: Remove outdated upstream package documentation (#1746)

* Remove outdated upstream package documentation

Upstream packages are now built through a Python script, 'build.py'
from the vyos-build repository:
https://github.com/vyos/vyos-build/tree/current/scripts/package-build/build.py

* Add build.py details to upstream-packages.rst

* Fix line length lint errors

1 files changed, 125 insertions, 56 deletions

diff --git a/docs/contributing/upstream-packages.rst b/docs/contributing/upstream-packages.rst
index 78fe3745..c740b190 100644
--- a/docs/contributing/upstream-packages.rst
+++ b/docs/contributing/upstream-packages.rst
@@ -1,4 +1,4 @@
-:lastproofread: 2025-11-30
+:lastproofread: 2026-01-30
 
 .. _upstream_packages:
 
@@ -7,84 +7,153 @@ Upstream Packages
 #################
 
 Many base system packages are pulled straight from Debian's ``main`` and
-``contrib`` repositories, but there are exceptions.
-
-This page lists those exceptions and briefly describes changes made to
-these packages. If you only want to build a fresh ISO image, you can skip
+``contrib`` repositories, but there are exceptions. If you only want to build
+a fresh ISO image, you can skip
 this section. This information may be useful for a deeper dive into VyOS.
 
-``vyos-netplug``
-----------------
 
-VyOS uses a modified version because the upstream release sometimes causes
-network interfaces to go down.
+.. stop_vyoslinter
+
+System packages that are not directly pulled from Debian are built through a 
+separate build system, ``build.py`` in the `vyos-build <https://github.com/vyos/vyos-build/tree/current/scripts/package-build>`__ repository.
+
+.. start_vyoslinter
+
+
+Overview
+========
+
+Previously, VyOS used Jenkins for building upstream packages. With the move away 
+from Jenkins, the build system was replaced with a Python-based solution using 
+``build.py`` and ``package.toml`` configuration files.
+
+Each package directory contains:
+
+- A ``package.toml`` configuration file that defines how the package is built.
+- A symlink to the common ``build.py`` script in the build system.
+
+
+Building Packages
+=================
+
+To build a package, navigate to the package directory and execute the 
+build script:
+
+.. code-block:: console
+
+   cd package-build/<package-name>
+   ./build.py
+
+The script will:
+
+1. Check out the source code from the configured repository.
+2. Apply any patches defined in the configuration.
+3. Execute pre-build hooks (if configured).
+4. Build the package using the specified build command.
+5. Generate both binary (``.deb``) packages and source tarballs.
+
+
+Package Configuration (package.toml)
+====================================
+
+Each package directory contains a ``package.toml`` file that defines the build 
+parameters. The key configuration fields are:
+
+**name**
+   The package name (e.g., ``frr``)
+
+**commit_id**
+   The specific commit, tag, or branch to check out from the source repository
+   (e.g., ``stable/10.5``)
+
+**scm_url**
+   The Git URL of the upstream source repository
+   (e.g., ``https://github.com/FRRouting/frr.git``)
+
+.. stop_vyoslinter
+**build_cmd**
+   The command to execute for building the package. This replaces what was 
+   previously defined in the Jenkins ``Jenkinsfile``.
+
+   Default if not specified: ``dpkg-buildpackage -uc -us -tc -F --source-option=--tar-ignore=.git --source-option=--tar-ignore=.github``
+
+   Example with custom build command:
+
+   .. code-block:: toml
+
+      build_cmd = "sudo dpkg -i ../*.deb; dpkg-buildpackage -us -uc -tc -b -Ppkg.frr.rtrlib,pkg.frr.lua"
+.. start_vyoslinter
+
+**pre_build_hook** (Optional)
+   A shell command or script that executes after the repository is checked out 
+   and before the build process begins. This allows you to perform preparatory 
+   tasks such as:
+
+   - Creating directories
+   - Copying files
+   - Running custom setup scripts
+   - Installing dependencies
+
+   Single command example:
 
-Source: https://github.com/vyos/vyos-netplug.
+   .. code-block:: toml
 
-VyOS may switch to ``systemd`` in the future. Building the package does not
-require a special procedure.
+      pre_build_hook = "echo 'Preparing build environment'"
 
-``keepalived``
---------------
+   Multi-line commands example:
 
-``keepalived`` is not updated to newer feature releases between Debian releases.
-VyoS builds it from source.
+   .. code-block:: toml
 
-Debian maintains the package in git, but the upstream tarball was imported
-without its original commit history. To allow merging new tags, we maintain
-a fork with packaging files imported from
-Debian: https://github.com/vyos/keepalived-upstream.
+      pre_build_hook = """
+        mkdir -p ../hello/vyos
+        mkdir -p ../vyos
+        cp example.txt ../vyos
+      """
 
-``strongswan``
---------------
+   Combined commands and scripts:
 
-VyOS's StrongSWAN build differs from upstream:
+   .. code-block:: toml
 
-- We disable the ``strongswan-nm`` package build because VyOS does not use
-  NetworkManager.
-- We merged patches for DMVPN.
+      pre_build_hook = "ls -l; ./script.sh"
 
-Source: https://github.com/vyos/vyos-strongswan
+**apply_patches** (Optional)
+   Boolean flag to control whether patches should be applied. Defaults to
+   ``True``.
 
-DMVPN patches were added in this commit:
-https://github.com/vyos/vyos-strongswan/commit/1cf12b0f2f921bfc51affa3b81226
+   .. code-block:: toml
 
-VyOS's op-mode scripts use the ``python-vici`` module, which is not included
-in Debian's build and is difficult to integrate. VyOS debianizes the module
-manually:
+      apply_patches = false
 
-1. Install ``stdeb`` from PyPI (for example: ``pip3 install stdeb``).
-2. ``cd vyos-strongswan``
-3. ``./configure --enable-python-eggs``
-4. ``cd src/libcharon/plugins/vici/python``
-5. ``make``
-6. ``python3 setup.py --command-packages=stdeb.command bdist_deb``
+**prepare_package** (Optional)
+   Boolean flag to enable package preparation. When set to ``True``, the 
+   ``install_data`` configuration is used.
 
-The package is created in the ``deb_dist`` directory.
+**install_data** (Optional)
+   Data used for package preparation when ``prepare_package`` is enabled.
 
-``mdns-repeater``
------------------
 
-This package does not exist in Debian. VyOS maintains a debianized fork at
-https://github.com/vyos/mdns-repeater.
+Example package.toml file
+===========================
 
-No special build procedure is required.
+Here's an example configuration for the FRRouting (FRR) package:
 
-``udp-broadcast-relay``
------------------------
+.. code-block:: toml
 
-This package does not exist in Debian. VyOS maintain a debianized fork at
-https://github.com/vyos/udp-broadcast-relay.
+   name = "frr"
+   commit_id = "stable/10.5"
+   scm_url = "https://github.com/FRRouting/frr.git"
+   build_cmd = "sudo dpkg -i ../*.deb; dpkg-buildpackage -us -uc -tc -b -Ppkg.frr.rtrlib,pkg.frr.lua"
 
-No special build procedure is required.
 
-``hvinfo``
-----------
+Build Output
+============
 
-A fork with packaging changes for VyOS is available
-at https://github.com/vyos/hvinfo.
+After running ``./build.py``, the following artifacts are generated in the 
+package directory:
 
-The original repository is at https://github.com/dmbaturin/hvinfo.
+- ``.deb`` files - Binary Debian packages ready for installation
+- ``.tar.gz`` files - Source tarballs of the checked-out repositories
+- Additional build artifacts as produced by the Debian build system
 
-It is an Ada program and requires GNAT and ``gprbuild``. Dependencies are
-properly specified; follow the suggestions from ``debuild``.
+The build script also creates build dependency packages (`*build-deps*.deb`), 
+which are automatically cleaned up after the build completes.