ARM: dts: stm32: Add STM32MP257F Evaluation 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 ...

Sync device tree with kernel v6.6-rc1.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/arch/arm/dts/stm32mp25-pinctrl.dtsi b/arch/arm/dts/stm32mp25-pinctrl.dtsi
new file mode 100644
index 0000000..d34a1d5
--- /dev/null
+++ b/arch/arm/dts/stm32mp25-pinctrl.dtsi
@@ -0,0 +1,38 @@
+// 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.
+ */
+#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 */
+		};
+	};
+};