Re: [PATCH v4 2/7] dt-bindings: mfd: Describe the BCM6846 PMC complex

[Rob Herring <robh@kernel.org>]

On Wed, Nov 11, 2026 at 12:00:43PM +0100, Linus Walleij wrote:
> The third generation Power Management Controller (PMC3) has
> different subdevices.
> 
> Identify the parent with the BCM6846-specific "brcm,bcm6846-pmc"
> compatible.
> 
> Describe the complex as a simple-mfd with a PMB bus child owning its
> register resource. Include the PMB power, clock and reset controllers and
> PVTMON, with its acquisition clock and reset resources.
> 
> Signed-off-by: Linus Walleij <linusw@kernel.org>
> ---
>  .../devicetree/bindings/mfd/brcm,bcm6846-pmc.yaml  | 87 ++++++++++++++++++++++
>  MAINTAINERS                                        |  1 +
>  2 files changed, 88 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/brcm,bcm6846-pmc.yaml b/Documentation/devicetree/bindings/mfd/brcm,bcm6846-pmc.yaml
> new file mode 100644
> index 000000000000..6082e30d37ec
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/brcm,bcm6846-pmc.yaml
> @@ -0,0 +1,87 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/brcm,bcm6846-pmc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Broadcom BCM6846 Power Management Controller
> +
> +maintainers:
> +  - Linus Walleij <linusw@kernel.org>
> +
> +description:
> +  The third generation Power Management Controller (PMC3) contains several
> +  register banks. This binding describes the Power Management Bus (PMB)
> +  interface within Procmon. The PMB child owns its register bank. The parent
> +  provides address translation and does not own a register bank.
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: brcm,bcm6846-pmc
> +      - const: simple-mfd
> +
> +  ranges:
> +    maxItems: 1
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 1
> +
> +patternProperties:
> +  '^bus@[0-9a-f]+$':
> +    $ref: /schemas/soc/bcm/brcm,bcm6846-pmb.yaml#
> +    description: PMB configuration, keyhole and address mapping registers

This causes the bus node to be validated twice (once here and once when 
applied by compatible). And then because the pmb schema does the same 
thing with its child nodes, those will be validated 3 times. Twice I can 
live with, 3 times not so much. The fix for all this is either merge the 
schemas to 1 file or do:

'^bus@[0-9a-f]+$':
  type: object
  additionalProperties: true
  properties:
    compatible:
      contains:
        const: brcm,bcm6846-pmb

  required:
    - compatible

That ensures the node contains enough to apply the child schema. 

Since there's 3 levels here, you could also do some combination of both.

Rob