dt-bindings: arm: rockchip: Add Anbernic RG353P and RG503

Add entry for the Anbernic RG353P and RG503 handheld devices.
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220906210324.28986-3-macroalpha82@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -30,6 +30,16 @@ properties:
           - const: amarula,vyasa-rk3288
           - const: rockchip,rk3288
 
+      - description: Anbernic RG353P
+        items:
+          - const: anbernic,rg353p
+          - const: rockchip,rk3566
+
+      - description: Anbernic RG503
+        items:
+          - const: anbernic,rg503
+          - const: rockchip,rk3566
+
       - description: Asus Tinker board
         items:
           - const: asus,rk3288-tinker