arm64: dts: st: add stm32mp257f-ev1 board support

Add STM32MP257F Evaluation board support. It embeds a STM32MP257FAI SoC,
with 4GB of DDR4, TSN switch (2+1 ports), 2*USB typeA, 1*USB2 typeC,
SNOR OctoSPI, mini PCIe, STPMIC2 for power distribution ...
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm64/boot/dts/Makefile

@@ -27,6 +27,7 @@ subdir-y += renesas
 subdir-y += rockchip
 subdir-y += socionext
 subdir-y += sprd
+subdir-y += st
 subdir-y += synaptics
 subdir-y += tesla
 subdir-y += ti

arch/arm64/boot/dts/st/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+dtb-$(CONFIG_ARCH_STM32) += stm32mp257f-ev1.dtb

arch/arm64/boot/dts/st/stm32mp25-pinctrl.dtsi

@@ -5,3 +5,34 @@
  */
 #include <dt-bindings/pinctrl/stm32-pinfunc.h>
 
+&pinctrl {
+	usart2_pins_a: usart2-0 {
+		pins1 {
+			pinmux = <STM32_PINMUX('A', 4, AF6)>; /* USART2_TX */
+			bias-disable;
+			drive-push-pull;
+			slew-rate = <0>;
+		};
+		pins2 {
+			pinmux = <STM32_PINMUX('A', 8, AF8)>; /* USART2_RX */
+			bias-disable;
+		};
+	};
+
+	usart2_idle_pins_a: usart2-idle-0 {
+		pins1 {
+			pinmux = <STM32_PINMUX('A', 4, ANALOG)>; /* USART2_TX */
+		};
+		pins2 {
+			pinmux = <STM32_PINMUX('A', 8, AF8)>; /* USART2_RX */
+			bias-disable;
+		};
+	};
+
+	usart2_sleep_pins_a: usart2-sleep-0 {
+		pins {
+			pinmux = <STM32_PINMUX('A', 4, ANALOG)>, /* USART2_TX */
+				 <STM32_PINMUX('A', 8, ANALOG)>; /* USART2_RX */
+		};
+	};
+};

arch/arm64/boot/dts/st/stm32mp257f-ev1.dts

+// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-3-Clause)
+/*
+ * Copyright (C) STMicroelectronics 2023 - All Rights Reserved
+ * Author: Alexandre Torgue <alexandre.torgue@foss.st.com> for STMicroelectronics.
+ */
+
+/dts-v1/;
+
+#include "stm32mp257.dtsi"
+#include "stm32mp25xf.dtsi"
+#include "stm32mp25-pinctrl.dtsi"
+#include "stm32mp25xxai-pinctrl.dtsi"
+
+/ {
+	model = "STMicroelectronics STM32MP257F-EV1 Evaluation Board";
+	compatible = "st,stm32mp257f-ev1", "st,stm32mp257";
+
+	aliases {
+		serial0 = &usart2;
+	};
+
+	chosen {
+		stdout-path = "serial0:115200n8";
+	};
+
+	memory@80000000 {
+		device_type = "memory";
+		reg = <0x0 0x80000000 0x1 0x0>;
+	};
+
+	reserved-memory {
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		fw@80000000 {
+			compatible = "shared-dma-pool";
+			reg = <0x0 0x80000000 0x0 0x4000000>;
+			no-map;
+		};
+	};
+};
+
+&usart2 {
+	pinctrl-names = "default", "idle", "sleep";
+	pinctrl-0 = <&usart2_pins_a>;
+	pinctrl-1 = <&usart2_idle_pins_a>;
+	pinctrl-2 = <&usart2_sleep_pins_a>;
+	status = "okay";
+};