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/sh/cpu/sh2/start.S

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2007,2008 Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
+ * Copyright (C) 2008 Renesas Solutions Corp.
+
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <asm-offsets.h>
+#include <config.h>
+
+	.text
+	.align	2
+
+	.global	_start
+_sh_start:
+	.long 0x00000010	/* Ppower ON reset PC*/
+	.long 0x00000000
+	.long 0x00000010	/* Manual reset PC */
+	.long 0x00000000
+_init:
+	mov.l	._lowlevel_init, r0
+100:	bsrf	r0
+	nop
+	bsr	1f
+	nop
+1:	sts	pr, r5
+	mov.l	._reloc_dst, r4
+	add	#(_sh_start-1b), r5
+	mov.l	._reloc_dst_end, r6
+
+2:	mov.l	@r5+, r1
+	mov.l	r1, @r4
+	add	#4, r4
+	cmp/hs	r6, r4
+	bf	2b
+
+	mov.l	._bss_start, r4
+	mov.l	._bss_end, r5
+	mov	#0, r1
+
+3:	mov.l	r1, @r4			/* bss clear */
+	add	#4, r4
+	cmp/hs	r5, r4
+	bf	3b
+
+	mov.l	._gd_init, r13		/* global data */
+	mov.l	._stack_init, r15	/* stack */
+
+	#TODO(sh maintainer): Fix this up to call the correct code
+	#mov.l	._sh_generic_init, r0
+	#jsr	@r0
+	nop
+
+loop:
+	bra	loop
+
+	.align	2
+
+._lowlevel_init:	.long	(lowlevel_init - (100b + 4))
+._reloc_dst:		.long	reloc_dst
+._reloc_dst_end:	.long	reloc_dst_end
+._bss_start:		.long	bss_start
+._bss_end:		.long	bss_end
+._gd_init:		.long	(_sh_start - GENERATED_GBL_DATA_SIZE)
+._stack_init:	.long	(_sh_start - GENERATED_GBL_DATA_SIZE - CONFIG_SYS_MALLOC_LEN - 16)
+#._sh_generic_init:	.long	sh_generic_init