Gpio controller:

Gpio controlled should be declared under ubus or periph single-bus parent

gpioc: gpioc {
	compatible = "brcm,bca-gpio";
            gpio-controller;
            #gpio-cells = <2>;
            reg = <0x0 0x500 0x0 0x40>;  /*offset from parent base, size of mapped region*/
            ngpios = <NUM_OF_GPIO_PINS>;   /* Should be defined on Family level */
            gpio-ranges = <&pincontroller 0 0 NUM_OF_GPIO_PINS>;
        };
			

Gpio Definition:
			
Gpio should be defined in the scope of the device/controller using it.
The gpio name must have one of the suffixes ("-gpio" or "-gpios")
Each gpio in the device tree is defined by three parameters:
The first is phandle to the gpio controller.
The second is the gpio number.
The third parameter is the flag. We will use a generic flag bitfield. All flag definitions are in include/dt-bindings/gpio/gpio.h. 			

&pon {
    status = "okay";
	pinctrl-0 = <&1pps_0_pins &RogueOnuEn_1_pins &WanNcoProgMClk_pins>;
	pinctrl-names = "default";
	txen-gpio = <&gpioc 34 GPIOF_ACTIVE_LOW> 
};

Once a device driver requires the gpio functionality it should call to standard linux API's

    struct gpio_desc * devm_gpiod_get(struct device *dev, const char *con_id, enum gpiod_flags flags)
Example:
    gpio_desc = devm_gpiod_get (node, "gio_function_name(w/o suffix)", GPIO_ASIS)

This will find the needed GPIO and request it from the gpio controller.

To set the GPIO  state to active (1) or not-active (0) use the following API:

    void gpiod_set_value(struct gpio_desc *desc, int value); 

To get current GPIO state use:
    int gpiod_get_value(const struct gpio_desc *desc);

The polarity is handled by this APIs.

To get current GPIO direction use:
    int gpiod_get_direction(struct gpio_desc *desc);

To set GPIO output direction and initial value of it use:
    int gpiod_direction_output(struct gpio_desc *desc, int value);
To set GPIO input direction use:
    int gpiod_direction_input(struct gpio_desc *desc);