dt-bindings: Add syscon YAML description

* System Controller Registers R/W driver

System controller node represents a register region containing a set

of miscellaneous registers. The registers are not cohesive enough to

represent as any specific type of device. The typical use-case is for

some other node's driver, or platform-specific code, to acquire a

reference to the syscon node (e.g. by phandle, node path, or search

using a specific compatible value), interrogate the node (or associated

OS driver) to determine the location of the registers, and access the

registers directly.

Required properties:

- compatible: Should contain "syscon".

- reg: the register region can be accessed from syscon

Optional property:

- reg-io-width: the size (in bytes) of the IO accesses that should be

  performed on the device.

- hwlocks: reference to a phandle of a hardware spinlock provider node.

Examples:

gpr: iomuxc-gpr@20e0000 {

	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";

	reg = <0x020e0000 0x38>;

	hwlocks = <&hwlock1 1>;

};

hwlock1: hwspinlock@40500000 {

	...

	reg = <0x40500000 0x1000>;

	#hwlock-cells = <1>;

};

# SPDX-License-Identifier: GPL-2.0

%YAML 1.2

---

$id: http://devicetree.org/schemas/mfd/syscon.yaml#

$schema: http://devicetree.org/meta-schemas/core.yaml#

title: System Controller Registers R/W Device Tree Bindings

description: |

  System controller node represents a register region containing a set

  of miscellaneous registers. The registers are not cohesive enough to

  represent as any specific type of device. The typical use-case is

  for some other node's driver, or platform-specific code, to acquire

  a reference to the syscon node (e.g. by phandle, node path, or

  search using a specific compatible value), interrogate the node (or

  associated OS driver) to determine the location of the registers,

  and access the registers directly.

maintainers:

  - Lee Jones <lee.jones@linaro.org>

select:

  properties:

    compatible:

      contains:

        enum:

          - syscon

  required:

    - compatible

properties:

  compatible:

    anyOf:

      - items:

        - enum:

          - allwinner,sun8i-a83t-system-controller

          - allwinner,sun8i-h3-system-controller

          - allwinner,sun8i-v3s-system-controller

          - allwinner,sun50i-a64-system-controller

        - const: syscon

      - contains:

          const: syscon

        additionalItems: true

  reg:

    maxItems: 1

  reg-io-width:

    description: |

      The size (in bytes) of the IO accesses that should be performed

      on the device.

    allOf:

      - $ref: /schemas/types.yaml#/definitions/uint32

      - enum: [ 1, 2, 4, 8 ]

  hwlocks:

    maxItems: 1

    description:

      Reference to a phandle of a hardware spinlock provider node.

required:

  - compatible

  - reg

unevaluatedProperties: false

examples:

  - |

    syscon: syscon@1c00000 {

        compatible = "allwinner,sun8i-h3-system-controller", "syscon";

        reg = <0x01c00000 0x1000>;

    };

  - |

    gpr: iomuxc-gpr@20e0000 {

        compatible = "fsl,imx6q-iomuxc-gpr", "syscon";

        reg = <0x020e0000 0x38>;

        hwlocks = <&hwlock1 1>;

    };

...

* Allwinner sun8i system controller

This file describes the bindings for the system controller present in

Allwinner SoC H3, A83T and A64.

The principal function of this syscon is to control EMAC PHY choice and

config.

Required properties for the system controller:

- reg: address and length of the register for the device.

- compatible: should be "syscon" and one of the following string:

		"allwinner,sun8i-h3-system-controller"

		"allwinner,sun8i-v3s-system-controller"

		"allwinner,sun50i-a64-system-controller"

		"allwinner,sun8i-a83t-system-controller"

Example:

syscon: syscon@1c00000 {

	compatible = "allwinner,sun8i-h3-system-controller", "syscon";

	reg = <0x01c00000 0x1000>;

};