docs: T8887: state SR-TE segment-list commit requirements

Per protocols_segment-routing.py verify(): a segment list needs at least
one index; each index needs an MPLS label or a NAI; an adjacency NAI
needs both source- and destination-identifier; a prefix identifier
needs an algorithm; IS-IS/OSPF import, adjacency/prefix, IPv4/IPv6 and
spf/strict-spf are mutually exclusive. Add a complete example.

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1 files changed, 24 insertions, 1 deletions

diff --git a/docs/configuration/protocols/segment-routing.md b/docs/configuration/protocols/segment-routing.md
index fccb2f40..c1bbe240 100644
--- a/docs/configuration/protocols/segment-routing.md
+++ b/docs/configuration/protocols/segment-routing.md
@@ -368,13 +368,16 @@ the path.
 ```{cfgcmd} set protocols segment-routing traffic-engineering database-import-protocol \<isis | ospf\>
 
 Select the IGP whose originated Traffic Engineering (TE) database is imported
-into the TED.
+into the TED. IS-IS and OSPF are mutually exclusive.
 ```
 
 ```{cfgcmd} set protocols segment-routing traffic-engineering segment-list \<name\>
 
 Define a named segment list. Each entry of the list is addressed by an index
 and describes one segment of the path.
+
+A segment list requires at least one index, and each index requires either
+an MPLS label or a NAI. Otherwise, the commit fails.
 ```
 
 ```{cfgcmd} set protocols segment-routing traffic-engineering segment-list \<name\> index \<index\> mpls label \<16-1048575\>
@@ -386,6 +389,10 @@ Set an MPLS label value for the given segment list index.
 
 Set the adjacency source address identifier (IPv4 or IPv6) for the given
 segment list index.
+
+An adjacency NAI requires both `source-identifier` and
+`destination-identifier`. A NAI is either an adjacency or a prefix, not
+both, and uses either IPv4 or IPv6, not both.
 ```
 
 ```{cfgcmd} set protocols segment-routing traffic-engineering segment-list \<name\> index \<index\> nai adjacency \<ipv4 | ipv6\> destination-identifier \<address\>
@@ -398,6 +405,9 @@ segment list index.
 
 Set an IGP prefix identifier (IPv4 or IPv6 prefix) for the given segment list
 index.
+
+A prefix identifier requires an `algorithm` (see the next command).
+Otherwise, the commit fails.
 ```
 
 ```{cfgcmd} set protocols segment-routing traffic-engineering segment-list \<name\> index \<index\> nai prefix \<ipv4 | ipv6\> prefix-identifier \<prefix\> algorithm \<spf | strict-spf\>
@@ -407,6 +417,19 @@ Select the IGP prefix algorithm style for the prefix identifier:
 - `spf`: Shortest Path First (SPF).
 - `strict-spf`: Strict SPF - ignore any possible local policy overriding the
   SPF along the path.
+
+`spf` and `strict-spf` are mutually exclusive.
+```
+
+Example of a segment list with one MPLS label, one adjacency, and one
+prefix segment:
+
+```none
+set protocols segment-routing traffic-engineering database-import-protocol isis
+set protocols segment-routing traffic-engineering segment-list SL1 index 10 mpls label 16001
+set protocols segment-routing traffic-engineering segment-list SL1 index 20 nai adjacency ipv4 source-identifier 192.0.2.1
+set protocols segment-routing traffic-engineering segment-list SL1 index 20 nai adjacency ipv4 destination-identifier 192.0.2.2
+set protocols segment-routing traffic-engineering segment-list SL1 index 30 nai prefix ipv4 prefix-identifier 198.51.100.1/32 algorithm spf
 ```
 
 ## Examples