boards/sam4s-xpro: introduce initial board support

Signed-off-by: dylad <dylan.laduranty@mesotic.com>

boards/sam4s-xpro/Makefile

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+MODULE = board
+
+include $(RIOTBASE)/Makefile.base

boards/sam4s-xpro/Makefile.features

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+CPU = sam4s
+CPU_MODEL = sam4sd32c
+
+# Put defined MCU peripherals here (in alphabetical order)
+FEATURES_PROVIDED += periph_gpio periph_gpio_irq
+FEATURES_PROVIDED += periph_timer
+FEATURES_PROVIDED += periph_uart

boards/sam4s-xpro/Makefile.include

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+# export this module and its includes
+INCLUDES  += -I$(RIOTBOARD)/sam4s-xpro/include
+
+# setup flasher (using openOCD)
+PROGRAMMER ?= openocd
+PROGRAMMERS_SUPPORTED += openocd edbg

boards/sam4s-xpro/dist/openocd.cfg

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+source [find board/atmel_sam4s_xplained_pro.cfg]
+$_TARGETNAME configure -rtos auto

boards/sam4s-xpro/doc.txt

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+/**
+@defgroup    boards_sam4s-xpro ATSAM4S Xplained Pro board
+@ingroup     boards
+@brief       Support for the ATSAM4S Xplained Pro board
+
+## Overview
+
+The `ATSAM4S Xplained Pro` is an evaluation board by Microchip (formerly Atmel)
+featuring a SAM4SD32 (Cortex-M4) SoC running up to 120 MHz. This MCU comes with
+160Kb of RAM and 2048Kb of flash memory.
+
+## Hardware
+
+![sam4s-xpro image](https://www.microchip.com/content/dam/mchp/mrt-dam/devtools/1801-atsam4s-xpro.jpg)
+
+
+### MCU
+| MCU        | ATSAM4SD32C      |
+|:------------- |:--------------------- |
+| Family | ARM Cortex-M4    |
+| Vendor | Microchip |
+| RAM        | 160Kb |
+| Flash      | 2048Kb             |
+| Frequency  | up to 120MHz |
+| FPU        | no                |
+| Timers | 2 three channels (16-bit)    |
+| ADCs       | 1x 12-bit (16 channels)           |
+| UARTs      | 2 UARTs (+ 2 USARTs shared with SPIs) |
+| SPIs       | 2 shared with USARTs                  |
+| I2Cs       | 2    |
+| Datasheet  | [Datasheet](https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/Atmel-11100-32-bitCortex-M4-Microcontroller-SAM4S_Datasheet.pdf) |
+| Board Manual   | [Board Manual](https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/UserGuides/Atmel-42075-SAM4S-Xplained-Pro_User-Guide.pdf)|
+
+### User Interface
+
+1 User button and 1 LED:
+
+| Device | PIN |
+|:------ |:--- |
+| LED0   | PC23 |
+| SW0 (button) | PA02 |
+
+### Flashing options
+By default, openOCD is used for both flashing and debugging.
+EDBG programmer is also available with:
+`PROGRAMMER=edbg BOARD=sam4s-xpro make -C tests/leds flash`
+
+ */

boards/sam4s-xpro/include/board.h

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+/*
+ * Copyright (C) 2025 Mesotic SAS
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_sam4s-xpro
+ * @{
+ *
+ * @file
+ * @brief       Board specific definitions for the Microchip SAM 4S Xplained Pro
+ *              board
+ *
+ * @author      Dylan Laduranty <dylan.laduranty@mesotic.com>
+ */
+
+#ifndef BOARD_H
+#define BOARD_H
+
+#include "cpu.h"
+#include "periph_conf.h"
+#include "periph_cpu.h"
+#include "periph/gpio.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    ztimer configuration
+ * @{
+ */
+#define CONFIG_ZTIMER_USEC_WIDTH        (16)
+/** @} */
+
+/**
+ * @name   LED pin definitions and handlers
+ * @{
+ */
+#define LED0_PIN            GPIO_PIN(PC, 23)
+
+#define LED0_ON             (PIOC->PIO_CODR  = PIO_PC23)
+#define LED0_OFF            (PIOC->PIO_SODR  = PIO_PC23)
+#define LED0_TOGGLE         ((PIOC->PIO_ODSR & PIO_PC23) ? LED0_ON : LED0_OFF)
+/** @} */
+
+/**
+ * @name SW0 (Button) pin definitions
+ * @{
+ */
+#define BTN0_PIN            GPIO_PIN(PA, 2)
+#define BTN0_MODE           GPIO_IN_PU
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BOARD_H */
+/** @} */

boards/sam4s-xpro/include/periph_conf.h

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+ /*
+ * Copyright (C) 2025 Mesotic SAS
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_sam4s-xpro
+ * @{
+ *
+ * @file
+ * @brief       Peripheral MCU configuration for SAM4S Xplained pro
+ *
+ * @author      Dylan Laduranty <dylan.laduranty@mesotic.com>
+ */
+
+#ifndef PERIPH_CONF_H
+#define PERIPH_CONF_H
+
+#include "periph_cpu.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    Clock configuration
+ * @{
+ */
+/* targeted system core clock */
+#define CLOCK_CORECLOCK     MHZ(120)
+/* external oscillator clock */
+#define CLOCK_EXT_OSC       MHZ(12)
+/* define PLL configuration
+ *
+ * The values must fulfill this equation:
+ * CORECLOCK = (EXT_OCS / PLL_DIV) * (PLL_MUL + 1)
+ */
+#define CLOCK_PLL_MUL       (9)
+#define CLOCK_PLL_DIV       (1)
+
+/* number of wait states before flash read and write operations */
+#define CLOCK_FWS           (5)         /* 5 is safe for 120 MHz */
+/** @} */
+
+/**
+ * @brief    Enable external oscillator for driving the slow clock
+ */
+#define CLOCK_SCLK_XTAL     (1)
+
+/**
+ * @name    Timer peripheral configuration
+ * @{
+ */
+static const timer_conf_t timer_config[] = {
+    { .dev = TC0, .id_ch0 = ID_TC0 },
+    { .dev = TC1, .id_ch0 = ID_TC3 }
+};
+
+#define TIMER_0_ISR         isr_tc0
+#define TIMER_1_ISR         isr_tc3
+
+#define TIMER_NUMOF         ARRAY_SIZE(timer_config)
+/** @} */
+
+/**
+ * @name    UART configuration
+ * @{
+ */
+static const uart_conf_t uart_config[] = {
+    {
+        .dev    = (Uart *)UART1,
+        .rx_pin = GPIO_PIN(PB, 2),
+        .tx_pin = GPIO_PIN(PB, 3),
+        .mux    = GPIO_MUX_A,
+        .pmc_id = ID_UART1,
+        .irqn   = UART1_IRQn
+    }
+};
+
+/* define interrupt vectors */
+#define UART_0_ISR          isr_uart1
+
+#define UART_NUMOF          ARRAY_SIZE(uart_config)
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_CONF_H */
+/** @} */