doc/device-tree-bindings/config.txt

The /config node (Configuration Options)
----------------------------------------

A number of run-time configuration options are provided in the /config node
of the control device tree. You can access these using fdtdec_get_config_int(),
fdtdec_get_config_bool() and fdtdec_get_config_string().

These options are designed to affect the operation of U-Boot at runtime.
Runtime-configuration items can help avoid proliferation of different builds
with only minor changes, e.g. enabling and disabling console output. Items
here should be those that can usefully be set by the build system after U-Boot
is built.

Available options are:

bootcmd (string)
	Allows overwriting of the boot command used by U-Boot on startup. If
	present, U-Boot uses this command instead. Note that this feature can
	work even if loading the environment is disabled, e.g. for security
	reasons. See also bootsecure.

bootdelay (int)
	This allows selecting of the U-Boot bootdelay, to control whether U-Boot
	waits on boot or for how long. This allows this option to be configured
	by the build system or by a previous-stage binary. For example, if the
	images is being packed for testing or a user holds down a button, it may
	allow a delay, but disable it for production.

u-boot,boot-led (string)
u-boot,error-led (string)
	This is used to specify the label for an LED to indicate an error and
	a successful boot, on supported hardware.

bootsecure (int)
	Indicates that U-Boot should use secure_boot_cmd() to run commands,
	rather than the normal CLI. This can be used in production images, to
	restrict the amount of parsing done or the options available, to cut
	back on the available surface for security attacks.

u-boot,efi-partition-entries-offset (int)
	If present, this provides an offset (in bytes, from the start of a
	device) that should be skipped over before the partition entries.
	This is used by the EFI/GPT partition implementation when a device
	is formatted.

	This setting will override any values configured via Kconfig.

kernel-offset (int)
	This allows setting the 'kernaddr' environment variable, used to select
	the address to load the kernel. It is useful for systems that use U-Boot
	to flash a device, so the scripts that do this know where to put the
	kernel to be flashed.

load-environment (int)
	Allows control over whether U-Boot loads its environment after
	relocation (0=no, 1 or not present=yes).

u-boot,mmc-env-offset (int)
u-boot,mmc-env-offset-redundant (int)
	If present, the values of the 'u-boot,mmc-env-offset' and/or
	of the u-boot,mmc-env-offset-redundant' properties overrides
	CONFIG_ENV_OFFSET and CONFIG_ENV_OFFSET_REDUND, respectively,
	for SD/MMC devices.

	Values are interpreted as the offset from the start of the
	device, specified in bytes.  It is assumed that the setting
	will point at the beginning of a LBA and values that are not
	LBA-aligned will be rounded up to the next LBA address.

u-boot,mmc-env-partition (int)
	if present, the environment shall be placed at the last
	CONFIG_ENV_SIZE blocks of the partition on the
	CONFIG_SYS_MMC_ENV_DEV.

	if u-boot,mmc-env-offset* is present, this setting will take
	precedence. In that case, only if the partition is not found,
	mmc-env-offset* will be tried.

u-boot,no-apm-finalize (bool)
	For x86 devices running on coreboot, this tells U-Boot not to lock
	down the Intel Management Engine (ME) registers. This allows U-Boot to
	access the hardware more fully for platforms that need it.

u-boot,no-keyboard (bool)
	Tells U-Boot not to expect an attached keyboard with a VGA console.

rootdisk-offset (int)
	This allows setting the 'rootdisk' environment variable, used to select
	the address to load the rootdisk. It is useful for systems that use
	U-Boot to flash a device, so the scripts that do this know where to put
	the root disk to be flashed.

silent-console (int)
	If present and non-zero, the console is silenced by default on boot.

u-boot,spl-payload-offset (int)
	If present (and SPL is controlled by the device-tree), this allows
	to override the CONFIG_SYS_SPI_U_BOOT_OFFS setting using a value
	from the device-tree.

sysreset-gpio (string)
	If present (and supported by the specific board), indicates a
	GPIO that can be set to trigger a system reset.  It is assumed
	that such a system reset will effect a complete platform reset,
	being roughly equivalent to a power-on reset.