Date:   Tue, 21 Dec 2021 13:55:33 -0400
From:   Rob Herring <robh@kernel.org>
To:     conor.dooley@microchip.com
Cc:     linus.walleij@linaro.org, bgolaszewski@baylibre.com,
        jassisinghbrar@gmail.com, paul.walmsley@sifive.com,
        palmer@dabbelt.com, aou@eecs.berkeley.edu, a.zummo@towertech.it,
        alexandre.belloni@bootlin.com, broonie@kernel.org,
        gregkh@linuxfoundation.org, thierry.reding@gmail.com,
        u.kleine-koenig@pengutronix.de, lee.jones@linaro.org,
        linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
        linux-pwm@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-crypto@vger.kernel.org, linux-rtc@vger.kernel.org,
        linux-spi@vger.kernel.org, linux-usb@vger.kernel.org,
        krzysztof.kozlowski@canonical.com, geert@linux-m68k.org,
        bin.meng@windriver.com, heiko@sntech.de, lewis.hanly@microchip.com,
        daire.mcnamara@microchip.com, ivan.griffin@microchip.com,
        atish.patra@wdc.com
Subject: Re: [PATCH v2 03/17] dt-bindings: soc/microchip: make
 systemcontroller a mfd
Message-ID: <YcIVFZSqt/JSuk3J@robh.at.kernel.org>
References: <20211217093325.30612-1-conor.dooley@microchip.com>
 <20211217093325.30612-4-conor.dooley@microchip.com>
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On Fri, Dec 17, 2021 at 09:33:11AM +0000, conor.dooley@microchip.com wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> Make the system controller on the Polarfire SoC
> a "simple,mfd" so that the services can be child
> nodes of the system controller node.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  .../microchip,mpfs-sys-controller.yaml        | 33 +++++++++++++++++--
>  1 file changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-sys-controller.yaml b/Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-sys-controller.yaml
> index f699772fedf3..014cb44b8f31 100644
> --- a/Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-sys-controller.yaml
> +++ b/Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-sys-controller.yaml
> @@ -13,13 +13,34 @@ description: |
>    The PolarFire SoC system controller is communicated with via a mailbox.
>    This document describes the bindings for the client portion of that mailbox.
>  
> -
>  properties:
>    mboxes:
>      maxItems: 1
>  
>    compatible:
> -    const: microchip,mpfs-sys-controller
> +    items:
> +      - const: microchip,mpfs-sys-controller
> +      - const: simple-mfd

'simple-mfd' means there is zero dependency on the parent for the child 
nodes. Isn't 'mboxes' a dependency?

> +
> +  hwrandom:
> +    type: object
> +
> +    properties:
> +      compatible:
> +        const: microchip,mpfs-rng
> +
> +    required:
> +      - compatible
> +
> +  sysserv:
> +    type: object
> +
> +    properties:
> +      compatible:
> +        const: microchip,mpfs-generic-service
> +
> +    required:
> +      - compatible

There's not really any need to have child nodes which have no resources. 
The driver for microchip,mpfs-sys-controller can create child devices.

Rob