Add subsubsections for possible boot methods and introduce a new section on eMMC boot support for the ast2600-evb and rainier-emmc machines, boot partitions assumptions and limitations. Acked-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Jan Luebbe <jlu@pengutronix.de> Reviewed-by: Andrew Jeffery <andrew@codeconstruct.com.au> Signed-off-by: Cédric Le Goater <clg@redhat.com>