dt-bindings: net: dsa: mediatek,mt7530: fix reset lines

- Add description for reset-gpios.
- Invalidate reset-gpios if mediatek,mcm is used. We cannot use multiple
reset lines at the same time.
- Invalidate mediatek,mcm if the compatible device is mediatek,mt7531.
There is no multi-chip module version of mediatek,mt7531.
- Require mediatek,mcm for mediatek,mt7621 as the compatible string is only
used for the multi-chip module version of MT7530.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/mediatek,mt7530.yaml

@@ -111,6 +111,11 @@ properties:
       switch is a part of the multi-chip module.
 
   reset-gpios:
+    description:
+      GPIO to reset the switch. Use this if mediatek,mcm is not used.
+      This property is optional because some boards share the reset line with
+      other components which makes it impossible to probe the switch if the
+      reset line is used.
     maxItems: 1
 
   reset-names:
@@ -165,6 +170,9 @@ allOf:
       required:
         - mediatek,mcm
     then:
+      properties:
+        reset-gpios: false
+
       required:
         - resets
         - reset-names
@@ -181,6 +189,22 @@ allOf:
         - core-supply
         - io-supply
 
+  - if:
+      properties:
+        compatible:
+          const: mediatek,mt7531
+    then:
+      properties:
+        mediatek,mcm: false
+
+  - if:
+      properties:
+        compatible:
+          const: mediatek,mt7621
+    then:
+      required:
+        - mediatek,mcm
+
 unevaluatedProperties: false
 
 examples: