boards: arm: add board support for mimxrt1015_evk

Add board support files for mimxrt1015_evk, the development board for
i.mxrt1015 (CM7) SoC.

- Add pinmux, dts, and doc.
- Tested samples: hello_world, philosophers, synchronization,
basic/blinky, basic/button.

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

boards/arm/mimxrt1015_evk/mimxrt1015_evk.dts

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2019, NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/dts-v1/;
+
+#include <nxp/nxp_rt.dtsi>
+
+/ {
+	model = "NXP MIMXRT1015-EVK board";
+	compatible = "nxp,mimxrt1015";
+
+	aliases {
+		gpio-1= &gpio1;
+		gpio-2= &gpio2;
+		gpio-3= &gpio3;
+		gpio-4= &gpio4;
+		gpio-5= &gpio5;
+		i2c-1 = &i2c1;
+		uart-1 = &uart1;
+		uart-4 = &uart4;
+		led0 = &green_led;
+		sw0 = &user_button;
+	};
+
+	chosen {
+		zephyr,console = &uart1;
+		zephyr,shell-uart = &uart1;
+	};
+
+	leds {
+		compatible = "gpio-leds";
+		green_led: led-1 {
+			gpios = <&gpio3 21 GPIO_INT_ACTIVE_LOW>;
+			label = "User LD1";
+		};
+	};
+
+	gpio_keys {
+		compatible = "gpio-keys";
+		user_button: button-1 {
+			label = "User SW4";
+			gpios = <&gpio2 9 GPIO_INT_ACTIVE_LOW>;
+		};
+	};
+};
+
+arduino_serial: &uart4 {};
+
+&flexspi0 {
+	reg = <0x402a8000 0x4000>, <0x60000000 0x1000000>;
+	at25sf128a: at25sf128a@0 {
+		compatible = "adesto,at25sf128a", "jedec,spi-nor";
+		reg = <0>;
+		status = "ok";
+	};
+};
+
+&i2c1 {
+	status = "ok";
+};
+
+&uart1 {
+	status = "ok";
+	current-speed = <115200>;
+};