let's use the same general names across projects so I don't have to think about multiple paths

firmware/app/src/main.c

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <zephyr/kernel.h>
+#include <zephyr/drivers/gpio.h>
+
+/* 1000 msec = 1 sec */
+#define SLEEP_TIME_MS 100
+
+/* The devicetree node identifier for the "led0" alias. */
+#define LED0_NODE DT_ALIAS(led0)
+
+/*
+ * A build error on this line means your board is unsupported.
+ * See the sample documentation for information on how to fix this.
+ */
+static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED0_NODE, gpios);
+
+int main(void)
+{
+    int ret;
+    bool led_state = true;
+
+    if (!gpio_is_ready_dt(&led))
+    {
+        return 0;
+    }
+
+    ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
+    if (ret < 0)
+    {
+        return 0;
+    }
+
+    while (1)
+    {
+        ret = gpio_pin_toggle_dt(&led);
+        if (ret < 0)
+        {
+            return 0;
+        }
+
+        led_state = !led_state;
+        printf("LED state: %s\n", led_state ? "ON" : "OFF");
+        k_msleep(SLEEP_TIME_MS);
+    }
+    return 0;
+}