dt-bindings: clock: renesas,rzg2l-cpg: Update #power-domain-cells = <1> for RZ/G3S

The driver will be modified (in the next commits) to be able to specify
individual power domain IDs for each IP.  The driver will still
support #power-domain-cells = <0>, thus, previous users are not
affected.

The #power-domain-cells = <1> has been instantiated only for RZ/G3S at
the moment, as individual platform clock drivers need to be adapted for
this to be supported on the rest of the SoCs.

Also, the description for #power-domain-cells is updated with links to
per-SoC power domain IDs.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240422105355.1622177-6-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/clock/renesas,rzg2l-cpg.yaml

@@ -57,7 +57,8 @@ properties:
       can be power-managed through Module Standby should refer to the CPG device
       node in their "power-domains" property, as documented by the generic PM
       Domain bindings in Documentation/devicetree/bindings/power/power-domain.yaml.
-    const: 0
+      The power domain specifiers defined in <dt-bindings/clock/r9a0*-cpg.h> could
+      be used to reference individual CPG power domains.
 
   '#reset-cells':
     description:
@@ -76,6 +77,21 @@ required:
 
 additionalProperties: false
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: renesas,r9a08g045-cpg
+    then:
+      properties:
+        '#power-domain-cells':
+          const: 1
+    else:
+      properties:
+        '#power-domain-cells':
+          const: 0
+
 examples:
   - |
     cpg: clock-controller@11010000 {