dt-bindings: soc: rockchip: add rockchip-io-domain.yaml object to grf.yaml

The rockchip-io-domain.txt file was converted to YAML.
IO Voltage Domain nodes are sub nodes of grf and pmugrf nodes.
Add rockchip-io-domain.yaml object to the grf.yaml file.

Signed-off-by: Johan Jonker <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Heiko Stuebner <[e-mail]>

Documentation/devicetree/bindings/soc/rockchip/grf.yaml

···
       - items:
           - enum:
               - rockchip,rk3288-sgrf
-              - rockchip,rv1108-pmugrf
               - rockchip,rv1108-usbgrf
           - const: syscon
       - items:
···
               - rockchip,rk3568-grf
               - rockchip,rk3568-pmugrf
               - rockchip,rv1108-grf
+              - rockchip,rv1108-pmugrf
           - const: syscon
           - const: simple-mfd
 
···
         compatible:
           contains:
             enum:
-              - rockchip,px30-pmugrf
               - rockchip,px30-grf
+              - rockchip,px30-pmugrf
+              - rockchip,rk3188-grf
               - rockchip,rk3228-grf
               - rockchip,rk3288-grf
               - rockchip,rk3328-grf
-              - rockchip,rk3368-pmugrf
               - rockchip,rk3368-grf
-              - rockchip,rk3399-pmugrf
+              - rockchip,rk3368-pmugrf
               - rockchip,rk3399-grf
+              - rockchip,rk3399-pmugrf
+              - rockchip,rv1108-grf
+              - rockchip,rv1108-pmugrf
 
     then:
       properties:
         io-domains:
-          description:
-            Documentation/devicetree/bindings/power/rockchip-io-domain.txt
+          type: object
+
+          $ref: "/schemas/power/rockchip-io-domain.yaml#"
+
+          unevaluatedProperties: false
 
 examples:
   - |