dt-bindings: riscv: add Zilsd and Zclsd extension descriptions

Add descriptions for the Zilsd (Load/Store pair instructions) and
Zclsd (Compressed Load/Store pair instructions) ISA extensions
which were ratified in commit f88abf1 ("Integrating load/store
pair for RV32 with the main manual") of the riscv-isa-manual.

Signed-off-by: Pincheng Wang <[e-mail]>
Reviewed-by: Nutty Liu <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paul Walmsley <[e-mail]>

Documentation/devicetree/bindings/riscv/extensions.yaml

···
             guarantee on LR/SC sequences, as ratified in commit b1d806605f87
             ("Updated to ratified state.") of the riscv profiles specification.
 
+        - const: zilsd
+          description:
+            The standard Zilsd extension which provides support for aligned
+            register-pair load and store operations in 32-bit instruction
+            encodings, as ratified in commit f88abf1 ("Integrating
+            load/store pair for RV32 with the main manual") of riscv-isa-manual.
+
+        - const: zclsd
+          description:
+            The Zclsd extension implements the compressed (16-bit) version of the
+            Load/Store Pair for RV32. As with Zilsd, this extension was ratified
+            in commit f88abf1 ("Integrating load/store pair for RV32 with the
+            main manual") of riscv-isa-manual.
+
         - const: zk
           description:
             The standard Zk Standard Scalar cryptography extension as ratified
···
             anyOf:
               - const: v
               - const: zve32x
+      # Zclsd depends on Zilsd and Zca
+      - if:
+          contains:
+            anyOf:
+              - const: zclsd
+        then:
+          contains:
+            allOf:
+              - const: zilsd
+              - const: zca
 
 allOf:
   # Zcf extension does not exist on rv64
···
           not:
             contains:
               const: zcf
+  # Zilsd extension does not exist on rv64
+  - if:
+      properties:
+        riscv,isa-base:
+          contains:
+            const: rv64i
+    then:
+      properties:
+        riscv,isa-extensions:
+          not:
+            contains:
+              const: zilsd
 
 additionalProperties: true
 ...