core/init: add early_init()

Add a function to initialize LEDs and UART in early boot.

core/lib/include/kernel_init.h

@@ -56,6 +56,15 @@ void kernel_init(void);
  */
 void board_init(void);
 
+/**
+ * @brief   Initialize debug LEDs and stdio
+ */
+#ifdef MODULE_CORE_INIT
+void early_init(void);
+#else
+static inline void early_init(void) {}
+#endif
+
 #ifdef __cplusplus
 }
 #endif

core/lib/init.c

@@ -29,6 +29,7 @@
 #include "log.h"
 #include "periph/pm.h"
 #include "thread.h"
+#include "stdio_base.h"
 
 #define ENABLE_DEBUG 0
 #include "debug.h"
@@ -102,3 +103,14 @@ void kernel_init(void)
 
     cpu_switch_context_exit();
 }
+
+void early_init(void)
+{
+    /* initialize leds */
+    if (IS_USED(MODULE_PERIPH_INIT_LEDS)) {
+        extern void led_init(void);
+        led_init();
+    }
+
+    stdio_init();
+}

drivers/periph_common/init.c

@@ -58,11 +58,6 @@
 void periph_init(void)
 {
 #ifdef MODULE_PERIPH_INIT
-    /* initialize leds */
-    if (IS_USED(MODULE_PERIPH_INIT_LEDS)) {
-        extern void led_init(void);
-        led_init();
-    }
     /* initialize buttonss */
     if (IS_USED(MODULE_PERIPH_INIT_BUTTONS)) {
         extern void button_init(void);