dt-bindings: soc: samsung: exynos-pmu: gs101: add google,pmu-intr-gen phandle

gs101 requires access to the pmu interrupt generation register region
which is exposed as a syscon. Update the exynos-pmu bindings documentation
to reflect this.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Link: https://lore.kernel.org/r/20250506-contrib-pg-cpu-hotplug-suspend2ram-fixes-v1-v4-2-9f64a2657316@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml

@@ -129,6 +129,11 @@ properties:
     description:
       Node for reboot method
 
+  google,pmu-intr-gen-syscon:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to PMU interrupt generation interface.
+
 required:
   - compatible
   - reg
@@ -189,6 +194,16 @@ allOf:
       properties:
         dp-phy: false
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - google,gs101-pmu
+    then:
+      required:
+        - google,pmu-intr-gen-syscon
+
 examples:
   - |
     #include <dt-bindings/clock/exynos5250.h>