ARM: mediatek: dts: Add uart to mt6592

This patch adds the uart ports and the uart clock to Mediateks
mt6592 SoC.
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm/boot/dts/mt6592.dtsi

@@ -78,6 +78,12 @@ rtc_clk: dummy32k {
 		#clock-cells = <0>;
 	};
 
+	uart_clk: dummy26m {
+		compatible = "fixed-clock";
+		clock-frequency = <26000000>;
+		#clock-cells = <0>;
+	};
+
 	timer: timer@10008000 {
 		compatible = "mediatek,mt6577-timer";
 		reg = <0x10008000 0x80>;
@@ -102,4 +108,36 @@ gic: interrupt-controller@10211000 {
 		reg = <0x10211000 0x1000>,
 		      <0x10212000 0x1000>;
 	};
+
+	uart0: serial@11002000 {
+		compatible = "mediatek,mt6577-uart";
+		reg = <0x11002000 0x400>;
+		interrupts = <GIC_SPI 51 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&uart_clk>;
+		status = "disabled";
+	};
+
+	uart1: serial@11003000 {
+		compatible = "mediatek,mt6577-uart";
+		reg = <0x11003000 0x400>;
+		interrupts = <GIC_SPI 52 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&uart_clk>;
+		status = "disabled";
+	};
+
+	uart2: serial@11004000 {
+		compatible = "mediatek,mt6577-uart";
+		reg = <0x11004000 0x400>;
+		interrupts = <GIC_SPI 53 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&uart_clk>;
+		status = "disabled";
+	};
+
+	uart3: serial@11005000 {
+		compatible = "mediatek,mt6577-uart";
+		reg = <0x11005000 0x400>;
+		interrupts = <GIC_SPI 54 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&uart_clk>;
+		status = "disabled";
+	};
 };