Convert documentation to rst format

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

This change contains update for doc/README.nokia_rx51 documentation file
with information how to load U-Boot image to device RAM without need to
flash it and also how to flash it into OneNAND via 0xFFFF flasher.

Signed-off-by: Pali Rohár <pali@kernel.org>

Since commit 25c5b6517854 ("Nokia RX-51: Do not try calling both ext2load
and ext4load") command ext4load is used for all ext2/3/4 fs variants.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

Enable U-Boot bootz command and update env scripts to try loading also
zImage file and to try booting via bootz command.

Update also lowlevel_init.S code for checking validity of zImage magic to
correctly relocate kernel in zImage format.

This change allows U-Boot to directly boot Linux kernel without need for
converting kernel image into U-Boot uImage format.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210618132704.32066-1-pali@kernel.org

Now when usbtty serial console is fixed in U-Boot enable CONFIG_USB_TTY for
Nokia RX-51 board by default.

Fix also USB product id as U-Boot ignores CONFIG_USBD_PRODUCTID macro and
include U-Boot string into USB product name to indicate usage of U-Boot.

CONFIG_CONSOLE_MUX is already used and U-Boot console is available for
all in/out devices. Therefore there is no need to have separate commands
'run sercon', 'run usbcon' and 'run vgacon', so remove them.

As space for U-Boot is limited to 256kB, enable CONFIG_OPTIMIZE_INLINING
and disable some other unused options so CONFIG_USB_TTY can be enabled.

Nokia RX-51 does not have easily accessible UART serial console so the only
option for easy debugging is to use device's keyboard+screen or this usbtty
serial console over USB.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Acked-by: Pavel Machek <pavel@ucw.cz>

This patch updates Nokia RX-51 README file.

Signed-off-by: Pali Rohár <pali@kernel.org>

Fix some typos, add information about setup_omap_atag, remove old suff
about ONENAND_SUPPORT and update guide for UBIFS.

Signed-off-by: Pali Rohár <pali@kernel.org>

Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Drop changes for PEP 4 following python tools]
Signed-off-by: Tom Rini <trini@ti.com>

Based on previous work by: Alistair Buxton <a.j.buxton@gmail.com>

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Cc: Ивайло Димитров <freemangordon@abv.bg>