ARM: dts: turris-omnia: Define S/PDIF audio card

Turris Omnia has GPIO51 exported on pin header U16, which works in S/PDIF
output mode. So define S/PDIF audio output card for this pin.
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

arch/arm/boot/dts/armada-385-turris-omnia.dts

@@ -105,6 +105,33 @@ sfp: sfp {
 		 */
 		status = "disabled";
 	};
+
+	sound {
+		compatible = "simple-audio-card";
+		simple-audio-card,name = "SPDIF";
+		simple-audio-card,format = "i2s";
+
+		simple-audio-card,cpu {
+			sound-dai = <&audio_controller 1>;
+		};
+
+		simple-audio-card,codec {
+			sound-dai = <&spdif_out>;
+		};
+	};
+
+	spdif_out: spdif-out {
+		#sound-dai-cells = <0>;
+		compatible = "linux,spdif-dit";
+	};
+};
+
+&audio_controller {
+	/* Pin header U16, GPIO51 in SPDIFO mode */
+	pinctrl-0 = <&spdif_pins>;
+	pinctrl-names = "default";
+	spdif-mode;
+	status = "okay";
 };
 
 &bm {