board: arm: Add board support for mimxrt1020_evk

Add board support files for mimxrt1020_evk, the development board for
i.MXRT1021 (CM7) SoC.

- Add pinmux, dts, doc.
- Code can be loaded to SRAM.
- Tested samples: hello_world, philosophers, synchronization,
basic/blinky, and basic/button.

Signed-off-by: Ryan QIAN <jianghao.qian@nxp.com>

boards/arm/mimxrt1020_evk/mimxrt1020_evk.dts

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2018, NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/dts-v1/;
+
+#include <nxp/nxp_rt.dtsi>
+
+/ {
+	model = "NXP MIMXRT1020-EVK board";
+	compatible = "nxp,mimxrt1021";
+
+	aliases {
+		gpio-1= &gpio1;
+		gpio-2= &gpio2;
+		gpio-3= &gpio3;
+		gpio-4= &gpio4;
+		gpio-5= &gpio5;
+		uart-1 = &uart1;
+		led0 = &green_led;
+		sw0 = &user_button;
+	};
+
+	chosen {
+#if defined(CONFIG_CODE_ITCM)
+		zephyr,flash = &itcm0;
+#elif defined(CONFIG_CODE_QSPI)
+		zephyr,flash = &qspi0;
+#endif
+		zephyr,sram = &dtcm0;
+		zephyr,console = &uart1;
+		zephyr,shell-uart = &uart1;
+	};
+
+	sdram0: memory@80000000 {
+		/* ISSI IS42S16160J-6TLI */
+		device_type = "memory";
+		reg = <0x80000000 0x2000000>;
+	};
+
+	leds {
+		compatible = "gpio-leds";
+		green_led: led-1 {
+			gpios = <&gpio1 5 GPIO_INT_ACTIVE_LOW>;
+			label = "User LD1";
+		};
+	};
+
+	gpio_keys {
+		compatible = "gpio-keys";
+		user_button: button-1 {
+			label = "User SW8";
+			gpios = <&gpio5 0 GPIO_INT_ACTIVE_LOW>;
+		};
+	};
+};
+
+&flexspi0 {
+	qspi0: qspi@60000000 {
+		/* ISSI IS25LP064A-JBLE */
+		reg = <0x60000000 0x800000>;
+		status = "ok";
+	};
+};
+
+&uart1 {
+	status = "ok";
+	current-speed = <115200>;
+};