dt-bindings: reset: npcm: add GCR syscon property

Describe syscon property that handles general control registers (GCR) in
Nuvoton BMC NPCM reset driver.
Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/reset/nuvoton,npcm750-reset.yaml

@@ -19,6 +19,10 @@ properties:
   '#reset-cells':
     const: 2
 
+  nuvoton,sysgcr:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: a phandle to access GCR registers.
+
   nuvoton,sw-reset-number:
     $ref: /schemas/types.yaml#/definitions/uint32
     minimum: 1
@@ -31,6 +35,7 @@ required:
   - compatible
   - reg
   - '#reset-cells'
+  - nuvoton,sysgcr
 
 additionalProperties: false
 
@@ -41,6 +46,7 @@ examples:
         compatible = "nuvoton,npcm750-reset";
         reg = <0xf0801000 0x70>;
         #reset-cells = <2>;
+        nuvoton,sysgcr = <&gcr>;
         nuvoton,sw-reset-number = <2>;
     };