* HDMI CEC GPIO driver

The HDMI CEC GPIO module supports CEC implementations where the CEC line
is hooked up to a pull-up GPIO line and - optionally - the HPD line is
hooked up to another GPIO line.

Required properties:
  - compatible: value must be "cec-gpio".
  - cec-gpios: gpio that the CEC line is connected to. The line should be
    tagged as open drain.

If the CEC line is associated with an HDMI receiver/transmitter, then the
following property is also required:

  - hdmi-phandle - phandle to the HDMI controller, see also cec.txt.

If the CEC line is not associated with an HDMI receiver/transmitter, then
the following property is optional:

  - hpd-gpios: gpio that the HPD line is connected to.

Example for the Raspberry Pi 3 where the CEC line is connected to
pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is
connected to pin 11 aka BCM17:

#include <dt-bindings/gpio/gpio.h>

cec-gpio {
       compatible = "cec-gpio";
       cec-gpios = <&gpio 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;
       hpd-gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
};