arm64: dts: exynos: Add initial E850-96 board support

E850-96 is a 96boards development board manufactured by WinLink. It
incorporates Samsung Exynos850 SoC, and is compatible with 96boards
mezzanine boards [1], as it follows 96boards standards.

This patch adds minimal support for E850-96 board. Next features are
enabled in board dts file and verified with minimal BusyBox rootfs:

 * User buttons
 * LEDs
 * Serial console
 * Watchdog timers
 * RTC
 * eMMC

[1] https://www.96boards.org/products/mezzanine/Signed-off-by: NSam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20220131130849.2667-3-semen.protsenko@linaro.orgSigned-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

arch/arm64/boot/dts/exynos/Makefile

@@ -3,4 +3,5 @@ dtb-$(CONFIG_ARCH_EXYNOS) += \
 	exynos5433-tm2.dtb	\
 	exynos5433-tm2e.dtb	\
 	exynos7-espresso.dtb	\
+	exynos850-e850-96.dtb	\
 	exynosautov9-sadk.dtb

arch/arm64/boot/dts/exynos/exynos850-e850-96.dts

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * WinLink E850-96 board device tree source
+ *
+ * Copyright (C) 2018 Samsung Electronics Co., Ltd.
+ * Copyright (C) 2021 Linaro Ltd.
+ *
+ * Device tree source file for WinLink's E850-96 board which is based on
+ * Samsung Exynos850 SoC.
+ */
+
+/dts-v1/;
+
+#include "exynos850.dtsi"
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
+#include <dt-bindings/leds/common.h>
+
+/ {
+	model = "WinLink E850-96 board";
+	compatible = "winlink,e850-96", "samsung,exynos850";
+
+	chosen {
+		stdout-path = &serial_0;
+	};
+
+	/*
+	 * RAM: 4 GiB (eMCP):
+	 *   - 2 GiB at 0x80000000
+	 *   - 2 GiB at 0x880000000
+	 *
+	 * 0xbab00000..0xbfffffff: secure memory (85 MiB).
+	 */
+	memory@80000000 {
+		device_type = "memory";
+		reg = <0x0 0x80000000 0x3ab00000>,
+		      <0x0 0xc0000000 0x40000000>,
+		      <0x8 0x80000000 0x80000000>;
+	};
+
+	gpio-keys {
+		compatible = "gpio-keys";
+		pinctrl-names = "default";
+		pinctrl-0 = <&key_voldown_pins &key_volup_pins>;
+
+		volume-down-key {
+			label = "Volume Down";
+			linux,code = <KEY_VOLUMEDOWN>;
+			gpios = <&gpa1 0 GPIO_ACTIVE_LOW>;
+		};
+
+		volume-up-key {
+			label = "Volume Up";
+			linux,code = <KEY_VOLUMEUP>;
+			gpios = <&gpa0 7 GPIO_ACTIVE_LOW>;
+		};
+	};
+
+	leds {
+		compatible = "gpio-leds";
+
+		/* HEART_BEAT_LED */
+		user_led1: led-1 {
+			label = "yellow:user1";
+			gpios = <&gpg2 2 GPIO_ACTIVE_HIGH>;
+			color = <LED_COLOR_ID_YELLOW>;
+			function = LED_FUNCTION_HEARTBEAT;
+			linux,default-trigger = "heartbeat";
+		};
+
+		/* eMMC_LED */
+		user_led2: led-2 {
+			label = "yellow:user2";
+			gpios = <&gpg2 3 GPIO_ACTIVE_HIGH>;
+			color = <LED_COLOR_ID_YELLOW>;
+			linux,default-trigger = "mmc0";
+		};
+
+		/* SD_LED */
+		user_led3: led-3 {
+			label = "white:user3";
+			gpios = <&gpg2 4 GPIO_ACTIVE_HIGH>;
+			color = <LED_COLOR_ID_WHITE>;
+			function = LED_FUNCTION_SD;
+			linux,default-trigger = "mmc2";
+		};
+
+		/* WIFI_LED */
+		wlan_active_led: led-4 {
+			label = "yellow:wlan";
+			gpios = <&gpg2 6 GPIO_ACTIVE_HIGH>;
+			color = <LED_COLOR_ID_YELLOW>;
+			function = LED_FUNCTION_WLAN;
+			linux,default-trigger = "phy0tx";
+			default-state = "off";
+		};
+
+		/* BLUETOOTH_LED */
+		bt_active_led: led-5 {
+			label = "blue:bt";
+			gpios = <&gpg2 7 GPIO_ACTIVE_HIGH>;
+			color = <LED_COLOR_ID_BLUE>;
+			function = LED_FUNCTION_BLUETOOTH;
+			linux,default-trigger = "hci0rx";
+			default-state = "off";
+		};
+	};
+
+	/*
+	 * RTC clock (XrtcXTI); external, must be 32.768 kHz.
+	 *
+	 * TODO: Remove this once RTC clock is implemented properly as part of
+	 *       PMIC driver.
+	 */
+	rtcclk: clock-rtcclk {
+		compatible = "fixed-clock";
+		clock-output-names = "rtcclk";
+		#clock-cells = <0>;
+		clock-frequency = <32768>;
+	};
+};
+
+&cmu_hsi {
+	clocks = <&oscclk>, <&rtcclk>,
+		 <&cmu_top CLK_DOUT_HSI_BUS>,
+		 <&cmu_top CLK_DOUT_HSI_MMC_CARD>,
+		 <&cmu_top CLK_DOUT_HSI_USB20DRD>;
+	clock-names = "oscclk", "rtcclk", "dout_hsi_bus",
+		      "dout_hsi_mmc_card", "dout_hsi_usb20drd";
+};
+
+&mmc_0 {
+	status = "okay";
+	mmc-hs200-1_8v;
+	mmc-hs400-1_8v;
+	cap-mmc-highspeed;
+	non-removable;
+	mmc-hs400-enhanced-strobe;
+	card-detect-delay = <200>;
+	clock-frequency = <800000000>;
+	bus-width = <8>;
+	samsung,dw-mshc-ciu-div = <3>;
+	samsung,dw-mshc-sdr-timing = <0 4>;
+	samsung,dw-mshc-ddr-timing = <2 4>;
+	samsung,dw-mshc-hs400-timing = <0 2>;
+
+	pinctrl-names = "default";
+	pinctrl-0 = <&sd0_clk_pins &sd0_cmd_pins &sd0_rdqs_pins &sd0_nreset_pins
+		     &sd0_bus1_pins &sd0_bus4_pins &sd0_bus8_pins>;
+};
+
+&oscclk {
+	clock-frequency = <26000000>;
+};
+
+&pinctrl_alive {
+	key_voldown_pins: key-voldown-pins {
+		samsung,pins = "gpa1-0";
+		samsung,pin-function = <EXYNOS_PIN_FUNC_EINT>;
+		samsung,pin-pud = <EXYNOS_PIN_PULL_NONE>;
+		samsung,pin-drv = <EXYNOS5420_PIN_DRV_LV1>;
+	};
+
+	key_volup_pins: key-volup-pins {
+		samsung,pins = "gpa0-7";
+		samsung,pin-function = <EXYNOS_PIN_FUNC_EINT>;
+		samsung,pin-pud = <EXYNOS_PIN_PULL_NONE>;
+		samsung,pin-drv = <EXYNOS5420_PIN_DRV_LV1>;
+	};
+};
+
+&rtc {
+	status = "okay";
+	clocks = <&cmu_apm CLK_GOUT_RTC_PCLK>, <&rtcclk>;
+	clock-names = "rtc", "rtc_src";
+};
+
+&serial_0 {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&uart1_pins>;
+};
+
+&usi_uart {
+	samsung,clkreq-on; /* needed for UART mode */
+	status = "okay";
+};
+
+&watchdog_cl0 {
+	status = "okay";
+};
+
+&watchdog_cl1 {
+	status = "okay";
+};