dt-bindings: arm: rockchip: Add Orange Pi 5 Plus

Add devicetree binding documentation for Orange Pi 5 Plus SBC made by
Xunlong.
Signed-off-by: Ondrej Jirman <megi@xff.cz>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231008130515.1155664-4-megi@xff.czSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -870,6 +870,11 @@ properties:
           - const: tronsmart,orion-r68-meta
           - const: rockchip,rk3368
 
+      - description: Xunlong Orange Pi 5 Plus
+        items:
+          - const: xunlong,orangepi-5-plus
+          - const: rockchip,rk3588
+
       - description: Xunlong Orange Pi R1 Plus / LTS
         items:
           - enum: