Renesas RZ/A1 combined Pin and GPIO controller

The Renesas SoCs of the RZ/A1 family feature a combined Pin and GPIO controller,
named "Ports" in the hardware reference manual.
Pin multiplexing and GPIO configuration is performed on a per-pin basis
writing configuration values to per-port register sets.
Each "port" features up to 16 pins, each of them configurable for GPIO
function (port mode) or in alternate function mode.
Up to 8 different alternate function modes exist for each single pin.

Pin controller node
-------------------

Required properties:
  - compatible
    this shall be "renesas,r7s72100-ports".

  - reg
    address base and length of the memory area where the pin controller
    hardware is mapped to.

Example:
Pin controller node for RZ/A1H SoC (r7s72100)

pinctrl: pin-controller@fcfe3000 {
	compatible = "renesas,r7s72100-ports";

	reg = <0xfcfe3000 0x4230>;
};

Sub-nodes
---------

The child nodes of the pin controller node describe a pin multiplexing
function or a GPIO controller alternatively.

- Pin multiplexing sub-nodes:
  A pin multiplexing sub-node describes how to configure a set of
  (or a single) pin in some desired alternate function mode.
  A single sub-node may define several pin configurations.
  A few alternate function require special pin configuration flags to be
  supplied along with the alternate function configuration number.
  The hardware reference manual specifies when a pin function requires
  "software IO driven" mode to be specified. To do so use the generic
  properties from the <include/linux/pinctrl/pinconf_generic.h> header file
  to instruct the pin controller to perform the desired pin configuration
  operation.
  Please refer to pinctrl-bindings.txt to get to know more on generic
  pin properties usage.

  The allowed generic formats for a pin multiplexing sub-node are the
  following ones:

  node-1 {
      pinmux = <PIN_ID_AND_MUX>, <PIN_ID_AND_MUX>, ... ;
      GENERIC_PINCONFIG;
  };

  node-2 {
      sub-node-1 {
          pinmux = <PIN_ID_AND_MUX>, <PIN_ID_AND_MUX>, ... ;
          GENERIC_PINCONFIG;
      };

      sub-node-2 {
          pinmux = <PIN_ID_AND_MUX>, <PIN_ID_AND_MUX>, ... ;
          GENERIC_PINCONFIG;
      };

      ...

      sub-node-n {
          pinmux = <PIN_ID_AND_MUX>, <PIN_ID_AND_MUX>, ... ;
          GENERIC_PINCONFIG;
      };
  };

  Use the second format when pins part of the same logical group need to have
  different generic pin configuration flags applied.

  Client sub-nodes shall refer to pin multiplexing sub-nodes using the phandle
  of the most external one.

  Eg.

  client-1 {
      ...
      pinctrl-0 = <&node-1>;
      ...
  };

  client-2 {
      ...
      pinctrl-0 = <&node-2>;
      ...
  };

  Required properties:
    - pinmux:
      integer array representing pin number and pin multiplexing configuration.
      When a pin has to be configured in alternate function mode, use this
      property to identify the pin by its global index, and provide its
      alternate function configuration number along with it.
      When multiple pins are required to be configured as part of the same
      alternate function they shall be specified as members of the same
      argument list of a single "pinmux" property.
      Helper macros to ease assembling the pin index from its position
      (port where it sits on and pin number) and alternate function identifier
      are provided by the pin controller header file at:
      <include/dt-bindings/pinctrl/r7s72100-pinctrl.h>
      Integers values in "pinmux" argument list are assembled as:
      ((PORT * 16 + PIN) | MUX_FUNC << 16)

  Optional generic properties:
    - input-enable:
      enable input bufer for pins requiring software driven IO input
      operations.
    - output-high:
      enable output buffer for pins requiring software driven IO output
      operations. output-low can be used alternatively, as line value is
      ignored by the driver.

  The hardware reference manual specifies when a pin has to be configured to
  work in bi-directional mode and when the IO direction has to be specified
  by software. Bi-directional pins are managed by the pin controller driver
  internally, while software driven IO direction has to be explicitly
  selected when multiple options are available.

  Example:
  A serial communication interface with a TX output pin and an RX input pin.

  &pinctrl {
	scif2_pins: serial2 {
		pinmux = <RZA1_PINMUX(3, 0, 6)>, <RZA1_PINMUX(3, 2, 4)>;
	};
  };

  Pin #0 on port #3 is configured as alternate function #6.
  Pin #2 on port #3 is configured as alternate function #4.

  Example 2:
  I2c master: both SDA and SCL pins need bi-directional operations

  &pinctrl {
	i2c2_pins: i2c2 {
		pinmux = <RZA1_PINMUX(1, 4, 1)>, <RZA1_PINMUX(1, 5, 1)>;
	};
  };

  Pin #4 on port #1 is configured as alternate function #1.
  Pin #5 on port #1 is configured as alternate function #1.
  Both need to work in bi-directional mode, the driver manages this internally.

  Example 3:
  Multi-function timer input and output compare pins.
  Configure TIOC0A as software driven input and TIOC0B as software driven
  output.

  &pinctrl {
	tioc0_pins: tioc0 {
		tioc0_input_pins {
			pinumx = <RZA1_PINMUX(4, 0, 2)>;
			input-enable;
		};

		tioc0_output_pins {
			pinmux = <RZA1_PINMUX(4, 1, 1)>;
			output-enable;
		};
	};
  };

  &tioc0 {
	...
	pinctrl-0 = <&tioc0_pins>;
	...
  };

  Pin #0 on port #4 is configured as alternate function #2 with IO direction
  specified by software as input.
  Pin #1 on port #4 is configured as alternate function #1 with IO direction
  specified by software as output.

- GPIO controller sub-nodes:
  Each port of the r7s72100 pin controller hardware is itself a GPIO controller.
  Different SoCs have different numbers of available pins per port, but
  generally speaking, each of them can be configured in GPIO ("port") mode
  on this hardware.
  Describe GPIO controllers using sub-nodes with the following properties.

  Required properties:
    - gpio-controller
      empty property as defined by the GPIO bindings documentation.
    - #gpio-cells
      number of cells required to identify and configure a GPIO.
      Shall be 2.
    - gpio-ranges
      Describes a GPIO controller specifying its specific pin base, the pin
      base in the global pin numbering space, and the number of controlled
      pins, as defined by the GPIO bindings documentation. Refer to
      Documentation/devicetree/bindings/gpio/gpio.txt file for a more detailed
      description.

  Example:
  A GPIO controller node, controlling 16 pins indexed from 0.
  The GPIO controller base in the global pin indexing space is pin 48, thus
  pins [0 - 15] on this controller map to pins [48 - 63] in the global pin
  indexing space.

  port3: gpio-3 {
	gpio-controller;
	#gpio-cells = <2>;
	gpio-ranges = <&pinctrl 0 48 16>;
  };

  A device node willing to use pins controlled by this GPIO controller, shall
  refer to it as follows:

  led1 {
	gpios = <&port3 10 GPIO_ACTIVE_LOW>;
  };
