bindings: gpio: Add support for sx150x IO expander

Semtech sx150x GPIO controller bindings

Required properties:

- compatible:

  - "sx1508q" for sx1508 GPIO controller

  - "sx1509q" for sx1509 GPIO controller

- #gpio-cells : Should be two.

  - first cell is the pin number

  - second cell is used to specify optional parameters (unused)

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

- reg: 7-bit I2C address.

- sx150x,reset_onprobe: If set to true, the driver will trigger

  a full reset of the chip at the beginning of the probe in order

  to place it in a known state.

- sx150x,oscio_is_gpo: If set to true, the driver will configure

  OSCIO as a GPO instead of as an oscillator, increasing the size

  of the GP(I)O pool created by this expander by one. The

  output-only GPO pin will be added at the end of the block.

- sx150x,pullup_ena: A bit-mask which enables or disables the pull-up

  resistor for each IO line in the expander. Setting the bit at

  position n will enable the pull-up for the IO at the corresponding

  offset. For chips with fewer than 16 IO pins, high-end bits are ignored.

- sx150x,pulldn_ena: A bit-mask which enables-or disables the pull-down

  resistor for each IO line in the expander. Setting the bit at position

  n will enable the pull-down for the IO at the corresponding offset.

  For chips with fewer than 16 IO pins, high-end bits are ignored.

- sx150x,float_ena: A bit-mask which enables-or disables open-drain

  operation for each IO line in the expander. Setting the bit at

  position n enables open-drain operation for the IO at the corresponding

  offset. Clearing the bit enables regular push-pull operation for that IO.

  For chips with fewer than 16 IO pins, high-end bits are ignored.

- sx150x,polarity: A bit-mask which enables polarity inversion for each IO line

  in the expander. Setting the bit at position n inverts the polarity of

  that IO line, while clearing it results in normal polarity. For chips with

  fewer than 16 IO pins, high-end bits are ignored.

- sx150x,reset_gpio: System GPIO number connected to NRESET of SX150x devices.

  If "sx150x,reset_onprobe" is true, then the reset_gpio is pulled from low

  to high to reset the SX150x device. (optional)

Example:

i2c@f9925000 {

   ioexp_gpios: io_exp@3e {

      #gpio-cells = <2>;

      gpio-controller;

      compatible = "sx1509q";

      reg = <0x3e>;

      sx150x,pullup_ena = <0x00>;

      sx150x,pulldn_ena = <0x00>;

      sx150x,float_ena  = <0x00>;

      sx150x,polarity = <0x00>;

      sx150x,reset_onprobe;

      sx150x,reset_gpio = <&msmgpio 138 0x00>;

      label = "ioexp-gpio";

   };

};

Usage:

gpio_test {

   compatible = "testcode";

   test_gpio = <&ioexp_gpios 5 0x00>;

};

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