Re: [PATCH v2 2/3] dt-bindings: serial: maxim,max310x: describe per-channel rs485 subnodes

[Krzysztof Kozlowski <krzk@kernel.org>]

On Mon, Jun 01, 2026 at 10:25:32AM +0000, Tapio Reijonen wrote:
> The MAX310x is a family of one- (max3107, max3108), two- (max3109) and
> four-channel (max14830) UARTs. The binding pulls in
> /schemas/serial/rs485.yaml at the chip level, describing a single set of
> RS-485 properties - enough for the single-channel parts, but a
> multi-channel chip can wire RS-485 differently on each channel.
> 
> Describe each channel as a "serial@N" subnode. Being a serial node (per
> serial.yaml) the channel carries the standard rs485.yaml properties and
> may also host a serial slave device. Constrain the channels per
> compatible: max3107 and max3108 have none and keep RS-485 on the chip
> node, max3109 has channels 0-1, and max14830 has 0-3. Chip-level rs485
> properties remain accepted and are the only form for the single-channel
> parts.
> 
> Signed-off-by: Tapio Reijonen <tapio.reijonen@vaisala.com>
> ---
>  .../devicetree/bindings/serial/maxim,max310x.yaml  | 90 ++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/maxim,max310x.yaml b/Documentation/devicetree/bindings/serial/maxim,max310x.yaml
> index 889eeaca64a027b4d9e8ec87bcf63fcc8fd9d55b..988864e7957416caea2d86c38957a894ce57c6fb 100644
> --- a/Documentation/devicetree/bindings/serial/maxim,max310x.yaml
> +++ b/Documentation/devicetree/bindings/serial/maxim,max310x.yaml
> @@ -40,6 +40,36 @@ properties:
>      minItems: 1
>      maxItems: 16
>  
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +patternProperties:
> +  "^serial@[0-3]$":
> +    type: object
> +    description:
> +      A single UART channel of a multi-channel variant. Describe the
> +      channel's RS-485 wiring here with the standard properties from
> +      /schemas/serial/rs485.yaml#; being a serial node, the channel may
> +      also host a serial slave device. Single-channel variants have no
> +      such subnode - their settings stay on the chip node.
> +
> +    allOf:
> +      - $ref: /schemas/serial/serial.yaml#
> +      - $ref: /schemas/serial/rs485.yaml#

So now both top-level node is serial and its children are. I don't think
that's correct. This binding should be split for two cases - single
channel and multi-channel, while multi-channels will require subnodes
(in the binding, keep driver backwards compatible).

Best regards,
Krzysztof