avionic design with actual uboot and tooling

submodule of avionic design uboot bootloader and with included tools to
get you started , read readme.md and readme-tk1-loader.md

u-boot/common/main.c

@@ -0,0 +1,70 @@
+/*
+ * (C) Copyright 2000
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/* #define	DEBUG	*/
+
+#include <common.h>
+#include <autoboot.h>
+#include <cli.h>
+#include <console.h>
+#include <version.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/*
+ * Board-specific Platform code can reimplement show_boot_progress () if needed
+ */
+__weak void show_boot_progress(int val) {}
+
+static void run_preboot_environment_command(void)
+{
+#ifdef CONFIG_PREBOOT
+	char *p;
+
+	p = getenv("preboot");
+	if (p != NULL) {
+# ifdef CONFIG_AUTOBOOT_KEYED
+		int prev = disable_ctrlc(1);	/* disable Control C checking */
+# endif
+
+		run_command_list(p, -1, 0);
+
+# ifdef CONFIG_AUTOBOOT_KEYED
+		disable_ctrlc(prev);	/* restore Control C checking */
+# endif
+	}
+#endif /* CONFIG_PREBOOT */
+}
+
+/* We come here after U-Boot is initialised and ready to process commands */
+void main_loop(void)
+{
+	const char *s;
+
+	bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");
+
+#ifdef CONFIG_VERSION_VARIABLE
+	setenv("ver", version_string);  /* set version variable */
+#endif /* CONFIG_VERSION_VARIABLE */
+
+	cli_init();
+
+	run_preboot_environment_command();
+
+#if defined(CONFIG_UPDATE_TFTP)
+	update_tftp(0UL, NULL, NULL);
+#endif /* CONFIG_UPDATE_TFTP */
+
+	s = bootdelay_process();
+	if (cli_process_fdt(&s))
+		cli_secure_boot_cmd(s);
+
+	autoboot_command(s);
+
+	cli_loop();
+	panic("No CLI available");
+}