On Wed, Apr 12, 2017 at 02:27:52PM -0300, Javier Martinez Canillas wrote:
> There are Device Tree source files defining a device node for the
> retu/tahvo I2C chip, but there isn't a DT binding document for it.
> 
> Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
> Acked-by: Rob Herring <robh@kernel.org>
> Acked-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Acked-by: Tony Lindgren <tony@atomide.com>
> Acked-by: Lee Jones <lee.jones@linaro.org>
> ---
> 
> Changes in v5:
> - Add missing properties for interrupts to DT binding doc (Rob Herring).
> - Add Rob Herring's Acked-by tag.
> - Add Aaro Koskinen's Acked-by tag.
> - Add Acked-by: Tony Lindgren <tony@atomide.com>'s Acked-by tag.
> - Add Lee Jones <lee.jones@linaro.org>'s Acked-by tag.
> 
> Changes in v4:
> - Use "dt-bindings: mfd:" prefix in subject line (Rob Herring).
> - Add information about what functions the device serve (Lee Jones).
> - Avoid using MFD in Device Tree (Lee Jones).
> 
> Changes in v3: None
> Changes in v2: None
> 
>  Documentation/devicetree/bindings/mfd/retu.txt | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/retu.txt
> 
> diff --git a/Documentation/devicetree/bindings/mfd/retu.txt b/Documentation/devicetree/bindings/mfd/retu.txt
> new file mode 100644
> index 000000000000..e1ea3a36a038
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/retu.txt
> @@ -0,0 +1,23 @@
> +* Device tree bindings for Nokia Retu and Tahvo multi-function device
> +
> +Retu and Tahvo are a multi-function devices found on Nokia Internet
> +Tablets (770, N800 and N810). The Retu chip provides watchdog timer
> +and power button control functionalities while Tahvo chip provides
> +USB transceiver functionality.
> +
> +Required properties:
> +- compatible:		"nokia,retu" or "nokia,tahvo"
> +- reg:			Specifies the I2C slave address of the ASIC chip

This should be "CBUS slave address". CBUS is a strange subset of I2C,
yet I'd like the distinction because 0x1 is not a valid I2C address.

> +- interrupts: 		The interrupt line the device is connected to
> +- interrupt-parent:	The parent interrupt controller
> +
> +Example:
> +
> +i2c0 {

To make it super clear, we are talking CBUS here, it might make sense to
add here:
+	compatible = "i2c-cbus-gpio";
+	...

? It could be argued that the above "i2c0" should be "cbus0" as well but
that is a separate issue, I'd think.

> +	retu: retu@1 {
> +		compatible = "nokia,retu";
> +		interrupt-parent = <&gpio4>;
> +		interrupts = <12 IRQ_TYPE_EDGE_RISING>;
> +		reg = <0x1>;
> +	};
> +};