wwan: T2529: migrate device from ttyUSB to usbXbY.YpZ.Z

During testing it was discovered that there is a well known problem (we had for
ethernet interfaces) also in the serial port world. They will be enumerated and
mapped to /dev/ttyUSBxxx differently from boot to boot. This is especially
painful on my development APU4 board which also has a Sierra Wireless MC7710
LTE module installed.

The serial port will toggle between ttyUSB2 and ttyUSB5 depending on the
amount of serial port extenders attached (FT4232H).

The shipped udev rule (/usr/lib/udev/rules.d/60-serial.rules) partly solves
this by enumerating the devices into /dev/serial/by-id folder with their name
and serial number - it's a very good idea but I've found that not all of the
FT4232H dongles have a serial number programmed - this leads to the situation
that when you plug in two cables with both having serial number 0 - only one
device symlink will appear - the previous one is always overwritten by the
latter one.

Derive /usr/lib/udev/rules.d/60-serial.rules and create a /dev/serial/by-bus
directory and group devices by attached USB root port.

  vyos@vyos:~$ find /dev/serial/by-bus/ -name usb* -exec basename {} \; | sort
  usb0b1.3p1.0
  usb0b1.3p1.2
  usb0b1.3p1.3
  usb0b2.4p1.0
  usb0b2.4p1.1
  usb0b2.4p1.2
  usb0b2.4p1.3

So we have USB root 0 with bus 1.3 and port 1.0. The enumeration is constant
accross reboots.

1 files changed, 7 insertions, 3 deletions

diff --git a/interface-definitions/interfaces-wirelessmodem.xml.in b/interface-definitions/interfaces-wirelessmodem.xml.in
index 91eee56ab..d5f2e04d7 100644
--- a/interface-definitions/interfaces-wirelessmodem.xml.in
+++ b/interface-definitions/interfaces-wirelessmodem.xml.in
@@ -46,12 +46,16 @@
           #include <include/interface-vrf.xml.i>
           <leafNode name="device">
             <properties>
-              <help>System device name (default: ttyUSB0)</help>
+              <help>Serial device </help>
               <completionHelp>
-                <script>ls -1 /dev | grep ttyUSB</script>
+                <script>ls -1 /dev /dev/serial/by-bus | grep -e ttyS[0-9]* -e usb[0-9]*</script>
               </completionHelp>
               <valueHelp>
-                <format>ttyXXX</format>
+                <format>ttySXX</format>
+                <description>System TTY device name</description>
+              </valueHelp>
+              <valueHelp>
+                <format>usbXbY.YpZ.Z</format>
                 <description>System TTY device name</description>
               </valueHelp>
             </properties>