mips: ath79: add AP121 reference board

This patch add board-level code and base DT for AP121.

Signed-off-by: Wills Wang <wills.wang@live.com>
[updated defconfig, enabled CONFIG_USE_PRIVATE_LIBGCC=y]
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/dts/ar933x.dtsi b/arch/mips/dts/ar933x.dtsi
new file mode 100644
index 0000000..11f60a2
--- /dev/null
+++ b/arch/mips/dts/ar933x.dtsi
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2015-2016 Wills Wang <wills.wang@live.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <dt-bindings/interrupt-controller/irq.h>
+#include "skeleton.dtsi"
+
+/ {
+	compatible = "qca,ar933x";
+
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		cpu@0 {
+			device_type = "cpu";
+			compatible = "mips,mips24Kc";
+			reg = <0>;
+		};
+	};
+
+	clocks {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		xtal: xtal {
+			#clock-cells = <0>;
+			compatible = "fixed-clock";
+			clock-output-names = "xtal";
+		};
+	};
+
+	pinctrl {
+		u-boot,dm-pre-reloc;
+		compatible = "qca,ar933x-pinctrl";
+		ranges;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		reg = <0x18040000 0x100>;
+	};
+
+	ahb {
+		compatible = "simple-bus";
+		ranges;
+
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		apb {
+			compatible = "simple-bus";
+			ranges;
+
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			uart0: uart@18020000 {
+				compatible = "qca,ar9330-uart";
+				reg = <0x18020000 0x20>;
+				interrupts = <128 IRQ_TYPE_LEVEL_HIGH>;
+
+				status = "disabled";
+			};
+		};
+
+		spi0: spi@1f000000 {
+			compatible = "qca,ar7100-spi";
+			reg = <0x1f000000 0x10>;
+			interrupts = <129 IRQ_TYPE_LEVEL_HIGH>;
+
+			status = "disabled";
+
+			#address-cells = <1>;
+			#size-cells = <0>;
+		};
+	};
+};