dt-bindings: net: sophgo,sg2044-dwmac: add phy mode restriction

As the ethernet controller of SG2044 and SG2042 only supports
RGMII phy. Add phy-mode property to restrict the value.

Also, since SG2042 has internal rx delay in its mac, make
only "rgmii-txid" and "rgmii-id" valid for phy-mode.

Fixes: e281c48a73 ("dt-bindings: net: sophgo,sg2044-dwmac: Add support for Sophgo SG2042 dwmac")
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251114003805.494387-2-inochiama@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/sophgo,sg2044-dwmac.yaml

@@ -70,6 +70,25 @@ required:
 
 allOf:
   - $ref: snps,dwmac.yaml#
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: sophgo,sg2042-dwmac
+    then:
+      properties:
+        phy-mode:
+          enum:
+            - rgmii-rxid
+            - rgmii-id
+    else:
+      properties:
+        phy-mode:
+          enum:
+            - rgmii
+            - rgmii-rxid
+            - rgmii-txid
+            - rgmii-id
 
 unevaluatedProperties: false