The UART controllers in most Rockchip SoCs are part of power domains
that are always powered on. These always powered on power domains have
typically not been described in the device tree.

Because these power domains have been left out of the device tree there
has not been any real need to properly describe the UART controllers
power domain of Rockchip SoCs.

On Rockchip RK3528 the UART controllers are spread out among the
described PD_RKVENC, PD_VO and PD_VPU power domains. However, one UART
controller belong to an undescribed always powered on power domain.

Add support to describe an optional power-domains for the UART
controllers.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
---
v2: New patch
---
 Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
index 8f1b7f704c5b..cb9da6c97afc 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
@@ -108,6 +108,9 @@ properties:
       parameter. Define this if your UART does not implement the busy functionality.
     type: boolean
 
+  power-domains:
+    maxItems: 1
+
   resets:
     minItems: 1
     maxItems: 2
-- 
2.50.1

On Wed, 23 Jul 2025 08:56:46 +0000, Jonas Karlman wrote:
> The UART controllers in most Rockchip SoCs are part of power domains
> that are always powered on. These always powered on power domains have
> typically not been described in the device tree.
> 
> Because these power domains have been left out of the device tree there
> has not been any real need to properly describe the UART controllers
> power domain of Rockchip SoCs.
> 
> On Rockchip RK3528 the UART controllers are spread out among the
> described PD_RKVENC, PD_VO and PD_VPU power domains. However, one UART
> controller belong to an undescribed always powered on power domain.
> 
> Add support to describe an optional power-domains for the UART
> controllers.
> 
> Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
> ---
> v2: New patch
> ---
>  Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml | 3 +++
>  1 file changed, 3 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>