boards/common/native: expose mock saul GPIO pins

When periph_gpio_mock is included, expose two LEDs via saul_gpio for
testing purposes.

This does not work with periph_gpio_linux because the hard-coded pins
are more dynamic for the native board.

Author: basilfx

boards/common/native/Makefile.dep

@@ -26,3 +26,9 @@ ifneq (,$(filter lvgl,$(USEPKG)))
 endif
 
 USEMODULE += native_drivers
+
+ifneq (,$(filter saul_default,$(USEMODULE)))
+  ifneq (,$(filter periph_gpio_mock,$(USEMODULE)))
+    USEMODULE += saul_gpio
+  endif
+endif

boards/common/native/include/gpio_params.h

@@ -0,0 +1,56 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Bas Stottelaar <basstottelaar@gmail.com>
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+#pragma once
+
+/**
+ * @ingroup     boards_common_native
+ * @{
+ *
+ * @file
+ * @brief       Board specific configuration of direct mapped GPIOs
+ *
+ * @author      Bas Stottelaar <basstottelaar@gmail.com>
+ */
+
+#include "board.h"
+#include "saul/periph.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if IS_USED(MODULE_PERIPH_GPIO_MOCK)
+/**
+ * @brief    GPIO pin configuration
+ *
+ * This is only used when MODULE_PERIPH_GPIO_MOCK is enabled to support
+ * arbitrary GPIO pin configurations for testing purposes. Other GPIO drivers
+ * would rely on pre-defined GPIO pin configurations, which are more dynamic
+ * for the native board.
+ *
+ * There is no feedback when using this configuration because it is only used
+ * to provide some mock SAUL GPIO capabilities.
+ */
+static const saul_gpio_params_t saul_gpio_params[] =
+{
+    {
+        .name = "LED 0 (mock)",
+        .pin = GPIO_PIN(0, 0),
+        .mode = GPIO_OUT
+    },
+    {
+        .name = "LED 1 (mock)",
+        .pin = GPIO_PIN(0, 1),
+        .mode = GPIO_OUT
+    }
+};
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */