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/arch/nios2/lib/bootm.c

@@ -0,0 +1,57 @@
+/*
+ * (C) Copyright 2003, Psyent Corporation <www.psyent.com>
+ * Scott McNutt <smcnutt@psyent.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+
+#define NIOS_MAGIC 0x534f494e /* enable command line and initrd passing */
+
+int do_bootm_linux(int flag, int argc, char * const argv[], bootm_headers_t *images)
+{
+	void (*kernel)(int, int, int, char *) = (void *)images->ep;
+	char *commandline = getenv("bootargs");
+	ulong initrd_start = images->rd_start;
+	ulong initrd_end = images->rd_end;
+	char *of_flat_tree = NULL;
+#if defined(CONFIG_OF_LIBFDT)
+	/* did generic code already find a device tree? */
+	if (images->ft_len)
+		of_flat_tree = images->ft_addr;
+#endif
+	if (!of_flat_tree && argc > 1)
+		of_flat_tree = (char *)simple_strtoul(argv[1], NULL, 16);
+	if (of_flat_tree)
+		initrd_end = (ulong)of_flat_tree;
+
+	/*
+	 * allow the PREP bootm subcommand, it is required for bootm to work
+	 */
+	if (flag & BOOTM_STATE_OS_PREP)
+		return 0;
+
+	if ((flag != 0) && (flag != BOOTM_STATE_OS_GO))
+		return 1;
+
+	/* flushes data and instruction caches before calling the kernel */
+	disable_interrupts();
+	flush_dcache_all();
+
+	debug("bootargs=%s @ 0x%lx\n", commandline, (ulong)&commandline);
+	debug("initrd=0x%lx-0x%lx\n", (ulong)initrd_start, (ulong)initrd_end);
+	/* kernel parameters passing
+	 * r4 : NIOS magic
+	 * r5 : initrd start
+	 * r6 : initrd end or fdt
+	 * r7 : kernel command line
+	 * fdt is passed to kernel via r6, the same as initrd_end. fdt will be
+	 * verified with fdt magic. when both initrd and fdt are used at the
+	 * same time, fdt must follow immediately after initrd.
+	 */
+	kernel(NIOS_MAGIC, initrd_start, initrd_end, commandline);
+	/* does not return */
+
+	return 1;
+}