dt-bindings: pinctrl: Add devicetree bindings for MT6797 SoC Pinctrl

* MediaTek MT6797 Pin Controller

The MediaTek's MT6797 Pin controller is used to control SoC pins.

Required properties:

- compatible: Value should be one of the following.

              "mediatek,mt6797-pinctrl", compatible with mt6797 pinctrl.

- reg:        Should contain address and size for gpio, iocfgl, iocfgb,

              iocfgr and iocfgt register bases.

- reg-names:  An array of strings describing the "reg" entries. Must

              contain "gpio", "iocfgl", "iocfgb", "iocfgr", "iocfgt".

- gpio-controller: Marks the device node as a gpio controller.

- #gpio-cells: Should be two. The first cell is the gpio pin number

               and the second cell is used for optional parameters.

Optional properties:

- interrupt-controller: Marks the device node as an interrupt controller.

- #interrupt-cells: Should be two.

- interrupts : The interrupt outputs from the controller.

Please refer to pinctrl-bindings.txt in this directory for details of the

common pinctrl bindings used by client devices.

Subnode format

A pinctrl node should contain at least one subnodes representing the

pinctrl groups available on the machine. Each subnode will list the

pins it needs, and how they should be configured, with regard to muxer

configuration, pullups, drive strength, input enable/disable and input schmitt.

    node {

        pinmux = <PIN_NUMBER_PINMUX>;

        GENERIC_PINCONFIG;

    };

Required properties:

- pinmux: Integer array, represents gpio pin number and mux setting.

    Supported pin number and mux varies for different SoCs, and are defined

    as macros in dt-bindings/pinctrl/<soc>-pinfunc.h directly.

Optional properties:

- GENERIC_PINCONFIG: is the generic pinconfig options to use, bias-disable,

    bias-pull, bias-pull-down, input-enable, input-schmitt-enable,

    input-schmitt-disable, output-enable output-low, output-high,

    drive-strength, and slew-rate are valid.

    Valid arguments for 'slew-rate' are '0' for no slew rate controlled and

    '1' for slower slew rate respectively. Valid arguments for 'drive-strength'

    is limited, such as 2, 4, 8, 12, or 16 in mA.

    Some optional vendor properties as defined are valid to specify in a

    pinconf subnode:

    - mediatek,tdsel: An integer describing the steps for output level shifter

      duty cycle when asserted (high pulse width adjustment). Valid arguments

      are from 0 to 15.

    - mediatek,rdsel: An integer describing the steps for input level shifter

      duty cycle when asserted (high pulse width adjustment). Valid arguments

      are from 0 to 63.

    - mediatek,pull-up-adv: An integer describing the code R1R0 as 0, 1, 2

      or 3 for the advanced pull-up resistors.

    - mediatek,pull-down-adv: An integer describing the code R1R0 as 0, 1, 2,

      or 3 for the advanced pull-down resistors.

Examples:

        pio: pinctrl@10005000 {

                compatible = "mediatek,mt6797-pinctrl";

                reg = <0 0x10005000 0 0x1000>,

                      <0 0x10002000 0 0x400>,

                      <0 0x10002400 0 0x400>,

                      <0 0x10002800 0 0x400>,

                      <0 0x10002C00 0 0x400>;

                reg-names = "gpio", "iocfgl", "iocfgb",

                            "iocfgr", "iocfgt";

                gpio-controller;

                #gpio-cells = <2>;

                uart1_pins_a: uart1 {

                        pins1 {

                                pinmux = <MT6797_GPIO232__FUNC_URXD1>,

                                         <MT6797_GPIO233__FUNC_UTXD1>;

                        };

                };

        };