ARM: dts: lpc4357-ea4357: add uart3

Enable UART3 that is routed to the J17 DSUB9 connector on
the EA4357 devkit.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>

arch/arm/boot/dts/lpc4357-ea4357-devkit.dts

@@ -205,6 +205,22 @@
 			bias-pull-down;
 		};
 	};
+
+	uart3_pins: uart3-pins {
+		uart3_rx_cfg {
+			pins = "p2_4";
+			function = "uart3";
+			input-schmitt-disable;
+			bias-disable;
+			input-enable;
+		};
+
+		uart3_tx_cfg {
+			pins = "p9_3";
+			function = "uart3";
+			bias-pull-down;
+		};
+	};
 };
 
 &enet_tx_clk {
@@ -231,3 +247,9 @@
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart0_pins>;
 };
+
+&uart3 {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&uart3_pins>;
+};