dt-bindings: arm: rockchip: Add NanoPC T6

Add the NanoPC T6, a single board computer from FriendlyElec
Signed-off-by: Thomas McKahan <tmckahan@singleboardsolutions.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230809112120.99-2-tmckahan@singleboardsolutions.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -227,6 +227,11 @@ properties:
               - friendlyarm,nanopi-r5s
           - const: rockchip,rk3568
 
+      - description: FriendlyElec NanoPC T6
+        items:
+          - const: friendlyarm,nanopc-t6
+          - const: rockchip,rk3588
+
       - description: GeekBuying GeekBox
         items:
           - const: geekbuying,geekbox