dt-bindings: mfd: Document smp-memram subnode for aspeed,ast2x00-scu

The platform initialisation code for the AST2600 implements the custom
SMP bringup protocol, and searches for the relevant compatible. As a
consequence, define the requisite node and the compatible string, which
in-turn tidies up the dtb check results.

Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260109-dev-dt-warnings-mfd-v1-1-1aabe37e9a14@codeconstruct.com.au
Signed-off-by: Lee Jones <lee@kernel.org>

Author: amboar

Documentation/devicetree/bindings/mfd/aspeed,ast2x00-scu.yaml

@@ -130,6 +130,23 @@ patternProperties:
           - description: silicon id information registers
           - description: unique chip id registers
 
+  '^smp-memram@[0-9a-f]+$':
+    description: Memory region used for the AST2600's custom SMP bringup protocol
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        const: aspeed,ast2600-smpmem
+
+      reg:
+        description: The SMP memory region
+        maxItems: 1
+
+    required:
+      - compatible
+      - reg
+
 required:
   - compatible
   - reg