dt-bindings: arm: rockchip: Add Radxa ROCK 5B+

The Radxa ROCK 5B+ is an improved version of the ROCK 5B.

Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -946,6 +946,11 @@ properties:
           - const: radxa,rock-5b
           - const: rockchip,rk3588
 
+      - description: Radxa ROCK 5B+
+        items:
+          - const: radxa,rock-5b-plus
+          - const: rockchip,rk3588
+
       - description: Radxa ROCK 5C
         items:
           - const: radxa,rock-5c