board: lenovo: ideapad-yoga-11: add Lenovo Ideapad Yoga 11 support

The Lenovo IdeaPad Yoga 11 is a hybrid laptop/tablet Windows RT-based
computer released in late 2012. The device uses a 1.3 GHz quad-core
Nvidia Tegra 3 chipset with 2 GB of RAM, features a 11.6 inch 1366x768
screen and 32/64 GB of internal memory that can be supplemented with
a microSDXC card slot, full size SD card slot and 2 full size USB 2.0
ports.

Tested-by: Jethro Bull <jethrob@hotmail.com>
Signed-off-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/doc/board/lenovo/ideapad-yoga-11.rst b/doc/board/lenovo/ideapad-yoga-11.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot for the Lenovo Ideapad Yoga 11 tablet
+============================================
+
+Quick Start
+-----------
+
+- Build U-Boot
+- Boot
+
+Build U-Boot
+------------
+
+.. code-block:: bash
+
+    $ export CROSS_COMPILE=arm-linux-gnueabi-
+    $ make ideapad-yoga-11_defconfig
+    $ make
+
+After the build succeeds, you will obtain the final ``u-boot-dtb-tegra.bin``
+image, ready for loading.
+
+Boot
+----
+
+Currently, U-Boot can be preloaded into RAM via the Fusée Gelée. To enter
+RCM protocol use ``power`` and ``volume up`` key combination from powered
+off device. The host PC should recognize an APX device.
+
+Built U-Boot ``u-boot-dtb-tegra.bin`` can be loaded from fusee-tools
+directory with
+
+.. code-block:: bash
+
+    $ ./run_bootloader.sh -s T30 -t ./bct/ideapad-yoga-11.bct
+
+To boot Linux, U-Boot will look for an ``extlinux.conf`` on MicroSD and then on
+eMMC. Additionally, if the Volume Down button is pressed while loading, the
+device will enter bootmenu. Bootmenu contains entries to mount MicroSD and eMMC
+as mass storage, fastboot, reboot, reboot RCM, poweroffand enter U-Boot console.