dt-bindings: arm: mediatek: mmsys: add power and gce properties

Power:
1. Add description for power-domains property.

GCE:
1. Add description for mboxes property.
2. Add description for mediatek,gce-client-reg property.
Signed-off-by: jason-jh.lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://lore.kernel.org/r/20220419033237.23405-2-rex-bc.chen@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.yaml

@@ -41,6 +41,30 @@ properties:
   reg:
     maxItems: 1
 
+  power-domains:
+    description:
+      A phandle and PM domain specifier as defined by bindings
+      of the power controller specified by phandle. See
+      Documentation/devicetree/bindings/power/power-domain.yaml for details.
+
+  mboxes:
+    description:
+      Using mailbox to communicate with GCE, it should have this
+      property and list of phandle, mailbox specifiers. See
+      Documentation/devicetree/bindings/mailbox/mtk-gce.txt for details.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+
+  mediatek,gce-client-reg:
+    description:
+      The register of client driver can be configured by gce with 4 arguments
+      defined in this property, such as phandle of gce, subsys id,
+      register offset and size.
+      Each subsys id is mapping to a base address of display function blocks
+      register which is defined in the gce header
+      include/dt-bindings/gce/<chip>-gce.h.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    maxItems: 1
+
   "#clock-cells":
     const: 1
 
@@ -56,9 +80,16 @@ additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/power/mt8173-power.h>
+    #include <dt-bindings/gce/mt8173-gce.h>
+
     mmsys: syscon@14000000 {
         compatible = "mediatek,mt8173-mmsys", "syscon";
         reg = <0x14000000 0x1000>;
+        power-domains = <&spm MT8173_POWER_DOMAIN_MM>;
         #clock-cells = <1>;
         #reset-cells = <1>;
+        mboxes = <&gce 0 CMDQ_THR_PRIO_HIGHEST>,
+                 <&gce 1 CMDQ_THR_PRIO_HIGHEST>;
+        mediatek,gce-client-reg = <&gce SUBSYS_1400XXXX 0 0x1000>;
     };