dt-bindings: display: mediatek: split: add compatible for MT8195

Add compatible string and GCE property for MT8195 SPLIT, of
which is operated by MDP3.

Signed-off-by: Moudy Ho <moudy.ho@mediatek.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Documentation/devicetree/bindings/display/mediatek/mediatek,split.yaml

@@ -23,6 +23,7 @@ properties:
     oneOf:
       - enum:
           - mediatek,mt8173-disp-split
+          - mediatek,mt8195-mdp3-split
       - items:
           - const: mediatek,mt6795-disp-split
           - const: mediatek,mt8173-disp-split
@@ -38,6 +39,21 @@ properties:
       the power controller specified by phandle. See
       Documentation/devicetree/bindings/power/power-domain.yaml for details.
 
+  mediatek,gce-client-reg:
+    description:
+      The register of display function block to be set by gce. There are 4 arguments,
+      such as gce node, subsys id, offset and register size. The subsys id that is
+      mapping to the register of display function blocks is defined in the gce header
+      include/dt-bindings/gce/<chip>-gce.h of each chips.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      items:
+        - description: phandle of GCE
+        - description: GCE subsys id
+        - description: register offset
+        - description: register size
+    maxItems: 1
+
   clocks:
     items:
       - description: SPLIT Clock
@@ -48,6 +64,17 @@ required:
   - power-domains
   - clocks
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: mediatek,mt8195-mdp3-split
+
+    then:
+      required:
+        - mediatek,gce-client-reg
+
 additionalProperties: false
 
 examples: