dt-bindings: arm-smmu: Allow 3 power domains on SM6375 MMU500

The SMMU on SM6375 requires 3 power domains to be active. Add an
appropriate description of that.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20221115152727.9736-2-konrad.dybcio@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>

Documentation/devicetree/bindings/iommu/arm,smmu.yaml

@@ -201,7 +201,8 @@ properties:
     maxItems: 7
 
   power-domains:
-    maxItems: 1
+    minItems: 1
+    maxItems: 3
 
   nvidia,memory-controller:
     description: |
@@ -366,6 +367,26 @@ allOf:
             - description: interface clock required to access smmu's registers
                 through the TCU's programming interface.
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: qcom,sm6375-smmu-500
+    then:
+      properties:
+        power-domains:
+          items:
+            - description: SNoC MMU TBU RT GDSC
+            - description: SNoC MMU TBU NRT GDSC
+            - description: SNoC TURING MMU TBU0 GDSC
+
+      required:
+        - power-domains
+    else:
+      properties:
+        power-domains:
+          maxItems: 1
+
 examples:
   - |+
     /* SMMU with stream matching or stream indexing */