mips: dts: ralink: mt7621: add serial1 and serial2 nodes

Add serial1 and serial2 nodes to define the existence of
the MT7621's second and third UARTs.
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Justin Swartz <justin.swartz@risingedge.co.za>
Reviewed-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/boot/dts/ralink/mt7621.dtsi

@@ -129,6 +129,46 @@ serial0: serial@c00 {
 			pinctrl-0 = <&uart1_pins>;
 		};
 
+		serial1: serial@d00 {
+			compatible = "ns16550a";
+			reg = <0xd00 0x100>;
+
+			reg-io-width = <4>;
+			reg-shift = <2>;
+
+			clocks = <&sysc MT7621_CLK_UART2>;
+
+			interrupt-parent = <&gic>;
+			interrupts = <GIC_SHARED 27 IRQ_TYPE_LEVEL_HIGH>;
+
+			no-loopback-test;
+
+			pinctrl-names = "default";
+			pinctrl-0 = <&uart2_pins>;
+
+			status = "disabled";
+		};
+
+		serial2: serial@e00 {
+			compatible = "ns16550a";
+			reg = <0xe00 0x100>;
+
+			reg-io-width = <4>;
+			reg-shift = <2>;
+
+			clocks = <&sysc MT7621_CLK_UART3>;
+
+			interrupt-parent = <&gic>;
+			interrupts = <GIC_SHARED 28 IRQ_TYPE_LEVEL_HIGH>;
+
+			no-loopback-test;
+
+			pinctrl-names = "default";
+			pinctrl-0 = <&uart3_pins>;
+
+			status = "disabled";
+		};
+
 		spi0: spi@b00 {
 			status = "disabled";