[PATCH v3 2/4] dt-bindings: serial: snps-dw-apb-uart: add Allwinner H616

[Krzysztof Kozlowski]

On Sat, Oct 24, 2026 at 02:22:24PM -0600, James Hilliard wrote:
> The H616 UART has 256-byte transmit and receive FIFOs, but its DesignWare
> component parameter register does not report the FIFO depth. Its optional
> register layout also differs from the generic DesignWare integration.
> 
> Add a specific compatible for the integration and allow the standard
> fifo-size property to describe the capacity. Require the documented
> 256-byte size for H616, retaining snps,dw-apb-uart as a fallback.
> 
> Signed-off-by: James Hilliard <james.hilliard1 at gmail.com>
> ---
>  .../devicetree/bindings/serial/snps-dw-apb-uart.yaml    | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> index e2ca126d58ba..0f8fd0485879 100644
> --- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> +++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> @@ -13,6 +13,18 @@ allOf:
>    - $ref: serial.yaml#
>    - $ref: rs485.yaml#
>  
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: allwinner,sun50i-h616-uart
> +    then:
> +      properties:
> +        fifo-size:
> +          const: 256
> +      required:
> +        - fifo-size

Why do you require fifo-size if is const? It is implied by the
compatible.

> +
>    - if:
>        properties:
>          compatible:
> @@ -60,6 +72,7 @@ properties:
>            - const: renesas,rzn1-uart
>        - items:
>            - enum:
> +              - allwinner,sun50i-h616-uart
>                - anlogic,dr1v90-uart
>                - brcm,bcm11351-dw-apb-uart
>                - brcm,bcm21664-dw-apb-uart
> @@ -120,6 +133,10 @@ properties:
>        - const: tx
>        - const: rx
>  
> +  fifo-size:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Transmit and receive FIFO capacity in bytes.

Drop property, not used by any of the devices here.

Best regards,
Krzysztof