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/arm/Kconfig.debug

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+menu "ARM debug"
+
+config DEBUG_LL
+	bool "Low-level debugging functions"
+	depends on !ARM64
+	help
+	  Say Y here to include definitions of printascii, printch, printhex
+	  in U-Boot.  This is helpful if you are debugging code that
+	  executes before the console is initialized.
+
+choice
+	prompt "Low-level debugging port"
+	depends on DEBUG_LL
+
+	config DEBUG_LL_UART_8250
+		bool "Low-level debugging via 8250 UART"
+		help
+		  Say Y here if you wish the debug print routes to direct
+		  their output to an 8250 UART.  You can use this option
+		  to provide the parameters for the 8250 UART rather than
+		  selecting one of the platform specific options above if
+		  you know the parameters for the port.
+
+		  This option is preferred over the platform specific
+		  options; the platform specific options are deprecated
+		  and will be soon removed.
+
+endchoice
+
+config DEBUG_LL_INCLUDE
+	string
+	depends on DEBUG_LL
+	default "debug/8250.S" if DEBUG_LL_UART_8250 || DEBUG_UART_8250
+	default "mach/debug-macro.S"
+
+# Compatibility options for 8250
+config DEBUG_UART_8250
+	bool
+
+config DEBUG_UART_PHYS
+	hex "Physical base address of debug UART"
+	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
+
+# This is not used in U-Boot
+config DEBUG_UART_VIRT
+	hex
+	default DEBUG_UART_PHYS
+	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
+
+config DEBUG_UART_8250_SHIFT
+	int "Register offset shift for the 8250 debug UART"
+	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
+	default 2
+
+config DEBUG_UART_8250_WORD
+	bool "Use 32-bit accesses for 8250 UART"
+	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
+	depends on DEBUG_UART_8250_SHIFT >= 2
+
+config DEBUG_UART_8250_FLOW_CONTROL
+	bool "Enable flow control for 8250 UART"
+	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
+
+endmenu