Re: [PATCH v10 01/10] dt-bindings: serial: Added secondary clock for RZ/T2H RSCI

[Rob Herring <robh@kernel.org>]

On Fri, May 23, 2025 at 04:24:05PM +0200, Thierry Bultel wrote:
> At boot, the default clock is the PCLKM core clock (synchronous
> clock, which is enabled by the bootloader).
> For different baudrates, the asynchronous clock input must be used.
> Clock selection is made by an internal register of RCSI.
> 
> Add the optional "sck", external clock input.
> 
> Also remove the unneeded serial0 alias from the dts example.
> 
> Signed-off-by: Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
> ---
> Changes v9->v10:
>  - mention sck in description
>  - no maxItems on clock-names
>  - fixed the #include dependency in dts example
> Changes v8->v9:
>  - typo in description
>  - named clocks 'operational' and 'bus', and added optional 'sck' clock
>  - uses value of 2nd core clock in example to break the dependency on cpg patch
> ---
>  .../bindings/serial/renesas,rsci.yaml           | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/serial/renesas,rsci.yaml b/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> index ea879db5f485..1bf255407df0 100644
> --- a/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> +++ b/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> @@ -35,10 +35,15 @@ properties:
>        - const: tei
>  
>    clocks:
> -    maxItems: 1
> +    minItems: 2
> +    maxItems: 3
>  
>    clock-names:
> -    const: fck # UART functional clock
> +    minItems: 2
> +    items:
> +      - const: operation
> +      - const: bus
> +      - const: sck # optional external clock input

You can't just change the clock names. What happens to users of 'fck'?

And you can't make additional entries required. What happens to users 
with only 1 clock defined?

Rob