ARM: dts: sun5i: hsg-h702: Enable side volume buttons with LRADC

The tablet has volume up/down buttons on the side, connected to the LRADC.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun5i-a13-hsg-h702.dts

@@ -45,6 +45,7 @@
 #include "sunxi-common-regulators.dtsi"
 
 #include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
 #include <dt-bindings/pinctrl/sun4i-a10.h>
 
 / {
@@ -96,6 +97,25 @@ &i2c2 {
 	status = "okay";
 };
 
+&lradc {
+	vref-supply = <&reg_ldo2>;
+	status = "okay";
+
+	button@200 {
+		label = "Volume Up";
+		linux,code = <KEY_VOLUMEUP>;
+		channel = <0>;
+		voltage = <200000>;
+	};
+
+	button@400 {
+		label = "Volume Down";
+		linux,code = <KEY_VOLUMEDOWN>;
+		channel = <0>;
+		voltage = <400000>;
+	};
+};
+
 &mmc0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&mmc0_pins_a>, <&mmc0_cd_pin_h702>;