board: htc: endeavoru: add One X support

The HTC One X is a touchscreen-based, slate-sized smartphone
designed and manufactured by HTC that runs the Android operating
system. The One X features a 4.7" display, an Nvidia Tegra 3
quad-core chip, 1 GB of RAM and non-extendable 32 GB of internal
storage. UART-A is default debug port.

Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com>
Tested-by: Ion Agorria <ion@agorria.com>
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/doc/board/htc/endeavoru.rst b/doc/board/htc/endeavoru.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot for the HTC One X (endeavoru)
+====================================
+
+``DISCLAMER!`` Moving your HTC ONe X to use U-Boot assumes
+replacement of the vendor hboot. Vendor android firmwares
+will no longer be able to run on the device.
+This replacement IS reversible.
+
+Quick Start
+-----------
+
+- Build U-Boot
+- Pack U-Boot into repart-block
+- Flash repart-block into the eMMC
+- Boot
+- Self Upgrading
+
+Build U-Boot
+------------
+
+.. code-block:: bash
+
+    $ export CROSS_COMPILE=arm-linux-gnueabi-
+    $ make endeavoru_defconfig
+    $ make
+
+After the build succeeds, you will obtain the final ``u-boot-dtb-tegra.bin``
+image, ready for flashing (but check the next section for additional
+adjustments).
+
+Pack U-Boot into repar-block
+----------------------------
+
+``DISCLAMER!`` All questions related to re-crypt work should be
+asked in re-crypt repo issues. NOT HERE!
+
+re-crypt is a small script which packs ``u-boot-dtb-tegra.bin`` in
+form usable by device. This process is required only on the first
+installation or to recover the device in case of a failed update.
+
+.. code-block:: bash
+
+    $ git clone https://github.com/clamor-s/re-crypt.git
+    $ cd re-crypt # place your u-boot-dtb-regra.bin here
+    $ ./re-crypt.sh -d endeavoru
+
+Script will produce you a ``repart-block.bin`` ready to flash.
+
+Flash repart-block into the eMMC
+--------------------------------
+
+``DISCLAMER!`` All questions related to NvFlash should be asked
+in the proper place. NOT HERE! Flashing repart-block will erase
+all your eMMC, so make a backup before!
+
+``repart-block.bin`` contains BCT and bootloader in encrypted state
+in form which can just be written RAW at the start of eMMC.
+
+.. code-block:: bash
+
+    $ wheelie --blob blob.bin
+    $ nvflash --resume --rawdevicewrite 0 1024 repart-block.bin
+
+Boot
+----
+
+After flashing ``repart-block.bin`` the device should reboot and turn
+itself off. This is normal behavior if no boot configuration is
+found.
+
+To boot Linux, U-Boot will look for an ``extlinux.conf`` configuration
+on eMMC. Additionally if Volume Down button is pressed while booting
+device will enter bootmenu. Bootmenu contains entries to mount eMMC as
+mass storage, fastboot, reboot, reboot RCM, poweroff, enter U-Boot
+console and update bootloader (check next chapter).
+
+Flashing ``repart-block.bin`` eliminates vendor restriction on eMMC
+and allows the user to use/partition it in any way the user desires.
+
+Self Upgrading
+--------------
+
+Place your ``u-boot-dtb-tegra.bin`` on the first partition of the
+eMMC (using ability of u-boot to mount it). Enter bootmenu, choose
+update bootloader option with Power button and U-Boot should update
+itself. Once the process is completed, U-Boot will ask to press any
+button to reboot.