reset: sti: Document sti-picophyreset controllers bindings.

STMicroelectronics STi family Sysconfig Picophy SoftReset Controller

=============================================================================

This binding describes a reset controller device that is used to enable and

disable on-chip PicoPHY USB2 phy(s) using "softreset" control bits found in

the STi family SoC system configuration registers.

The actual action taken when softreset is asserted is hardware dependent.

However, when asserted it may not be possible to access the hardware's

registers and after an assert/deassert sequence the hardware's previous state

may no longer be valid.

Please refer to Documentation/devicetree/bindings/reset/reset.txt

for common reset controller binding usage.

Required properties:

- compatible: Should be "st,stih407-picophyreset"

- #reset-cells: 1, see below

Example:

	picophyreset: picophyreset-controller {

		compatible = "st,stih407-picophyreset";

		#reset-cells = <1>;

	};

Specifying picophyreset control of devices

=======================================

Device nodes should specify the reset channel required in their "resets"

property, containing a phandle to the picophyreset device node and an

index specifying which channel to use, as described in

Documentation/devicetree/bindings/reset/reset.txt.

Example:

	usb2_picophy0: usbpicophy@0 {

		resets = <&picophyreset STIH407_PICOPHY0_RESET>;

	};

Macro definitions for the supported reset channels can be found in:

include/dt-bindings/reset-controller/stih407-resets.h