DTS to add GPIO keys as overlay on the Raspberry Pi

rpi_gpio_keys.dts

/dts-v1/;
/plugin/;
/ {
        compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709";

        fragment@0 {
                target-path = "/soc";
                __overlay__ {
                        keypad: keypad {
                                compatible = "gpio-keys";
                                button@2 {
                                        label = "Test BTN0";
                                        linux,code = <0x100>;
                                        gpios = <&gpio 2 0>;
                                };
                                button@3 {
                                        label = "Test BTN1";
                                        linux,code = <0x101>;
                                        gpios = <&gpio 3 0>;
                                };
                        };
                };
        };
};