Kernel-4.18.0-80.el8_raspberrypi,firmware-gpio

Raspberry Pi GPIO expander

The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The
firmware exposes a mailbox interface that allows the ARM core to control the
GPIO lines on the expander.

The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi
firmware node.

Required properties:

• compatible : Should be “raspberrypi,firmware-gpio”
• gpio-controller : Marks the device node as a gpio controller
• #gpio-cells : Should be two. The first cell is the pin number, and
  the second cell is used to specify the gpio polarity:
  0 = active high
  1 = active low

Example:

firmware: firmware-rpi {
compatible = “raspberrypi,bcm2835-firmware”;
mboxes = <&mailbox>;

expgpio: gpio {
     compatible = "raspberrypi,firmware-gpio";
     gpio-controller;
     #gpio-cells = <2>;
 };

};