samples: drivers: video: add DT_HAS_CHOSEN() safeguards

Add macros giving hints to users using #error, about what might be
missing to build and run the samples, such as a missing "chosen"
devicetree node.

Signed-off-by: Josuah Demangeon <me@josuah.net>

Author: josuah

samples/drivers/video/capture/src/main.c

@@ -22,6 +22,10 @@ LOG_MODULE_REGISTER(main, LOG_LEVEL_DBG);
 LOG_MODULE_REGISTER(main, CONFIG_LOG_DEFAULT_LEVEL);
 #endif
 
+#if !DT_HAS_CHOSEN(zephyr_camera)
+#error No camera chosen in devicetree. Missing "--shield" or "--snippet video-sw-generator" flag?
+#endif
+
 #if DT_HAS_CHOSEN(zephyr_display)
 static inline int display_setup(const struct device *const display_dev, const uint32_t pixfmt)
 {

samples/drivers/video/capture_to_lvgl/src/main.c

@@ -14,6 +14,14 @@
 
 LOG_MODULE_REGISTER(main, CONFIG_LOG_DEFAULT_LEVEL);
 
+#if !DT_HAS_CHOSEN(zephyr_camera)
+#error No camera chosen in devicetree. Missing "--shield" or "--snippet video-sw-generator" flag?
+#endif
+
+#if !DT_HAS_CHOSEN(zephyr_display)
+#error No display chosen in devicetree. Missing "--shield" flag?
+#endif
+
 int main(void)
 {
 	struct video_buffer *buffers[2];