dt-bindings: serial: snps-dw-apb-uart: Add Rockchip RK1808

Add a Rockchip RK1808 compatible.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210516230551.12469-3-afaerber@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
index 88bf4ad..b49fda5 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
@@ -23,6 +23,7 @@
       - items:
           - enum:
               - rockchip,px30-uart
+              - rockchip,rk1808-uart
               - rockchip,rk3036-uart
               - rockchip,rk3066-uart
               - rockchip,rk3188-uart