doc: android: Convert to Sphinx format

Convert Android documentation from regular txt format to Sphinx (RST).
Also add Android index.rst file and reference it in root index.rst, so
that Android documentation is visible.

Test:

    $ make htmldocs
    $ xdg-open doc/output/index.html

Signed-off-by: Sam Protsenko <joe.skb7@gmail.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

1 files changed, 206 insertions, 0 deletions

diff --git a/doc/android/fastboot.rst b/doc/android/fastboot.rst
new file mode 100644
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+.. SPDX-License-Identifier: GPL-2.0+
+
+Android Fastboot
+================
+
+Overview
+--------
+
+The protocol that is used over USB and UDP is described in [1]_.
+
+The current implementation supports the following standard commands:
+
+- ``boot``
+- ``continue``
+- ``download``
+- ``erase`` (if enabled)
+- ``flash`` (if enabled)
+- ``getvar``
+- ``reboot``
+- ``reboot-bootloader``
+- ``set_active`` (only a stub implementation which always succeeds)
+
+The following OEM commands are supported (if enabled):
+
+- ``oem format`` - this executes ``gpt write mmc %x $partitions``
+
+Support for both eMMC and NAND devices is included.
+
+Client installation
+-------------------
+
+The counterpart to this is the fastboot client which can be found in
+Android's ``platform/system/core`` repository in the fastboot
+folder. It runs on Windows, Linux and OSX. The fastboot client is
+part of the Android SDK Platform-Tools and can be downloaded from [2]_.
+
+Board specific
+--------------
+
+USB configuration
+^^^^^^^^^^^^^^^^^
+
+The fastboot gadget relies on the USB download gadget, so the following
+options must be configured:
+
+::
+
+   CONFIG_USB_GADGET_DOWNLOAD
+   CONFIG_USB_GADGET_VENDOR_NUM
+   CONFIG_USB_GADGET_PRODUCT_NUM
+   CONFIG_USB_GADGET_MANUFACTURER
+
+NOTE: The ``CONFIG_USB_GADGET_VENDOR_NUM`` must be one of the numbers
+supported by the fastboot client. The list of vendor IDs supported can
+be found in the fastboot client source code.
+
+General configuration
+^^^^^^^^^^^^^^^^^^^^^
+
+The fastboot protocol requires a large memory buffer for
+downloads. This buffer should be as large as possible for a
+platform. The location of the buffer and size are set with
+``CONFIG_FASTBOOT_BUF_ADDR`` and ``CONFIG_FASTBOOT_BUF_SIZE``. These
+may be overridden on the fastboot command line using ``-l`` and
+``-s``.
+
+Fastboot environment variables
+------------------------------
+
+Partition aliases
+^^^^^^^^^^^^^^^^^
+
+Fastboot partition aliases can also be defined for devices where GPT
+limitations prevent user-friendly partition names such as ``boot``, ``system``
+and ``cache``.  Or, where the actual partition name doesn't match a standard
+partition name used commonly with fastboot.
+
+The current implementation checks aliases when accessing partitions by
+name (flash_write and erase functions).  To define a partition alias
+add an environment variable similar to::
+
+    fastboot_partition_alias_<alias partition name>=<actual partition name>
+
+for example::
+
+    fastboot_partition_alias_boot=LNX
+
+Variable overrides
+^^^^^^^^^^^^^^^^^^
+
+Variables retrived through ``getvar`` can be overridden by defining
+environment variables of the form ``fastboot.<variable>``. These are
+looked up first so can be used to override values which would
+otherwise be returned. Using this mechanism you can also return types
+for NAND filesystems, as the fully parameterised variable is looked
+up, e.g.::
+
+    fastboot.partition-type:boot=jffs2
+
+Boot command
+^^^^^^^^^^^^
+
+When executing the fastboot ``boot`` command, if ``fastboot_bootcmd`` is set
+then that will be executed in place of ``bootm <CONFIG_FASTBOOT_BUF_ADDR>``.
+
+Partition Names
+---------------
+
+The Fastboot implementation in U-Boot allows to write images into disk
+partitions. Target partitions are referred on the host computer by
+their names.
+
+For GPT/EFI the respective partition name is used.
+
+For MBR the partitions are referred by generic names according to the
+following schema::
+
+    <device type><device index letter><partition index>
+
+Example: ``hda3``, ``sdb1``, ``usbda1``.
+
+The device type is as follows:
+
+  * IDE, ATAPI and SATA disks: ``hd``
+  * SCSI disks: ``sd``
+  * USB media: ``usbd``
+  * MMC and SD cards: ``mmcsd``
+  * Disk on chip: ``docd``
+  * other: ``xx``
+
+The device index starts from ``a`` and refers to the interface (e.g. USB
+controller, SD/MMC controller) or disk index. The partition index starts
+from ``1`` and describes the partition number on the particular device.
+
+Writing Partition Table
+-----------------------
+
+Fastboot also allows to write the partition table to the media. This can be
+done by writing the respective partition table image to a special target
+"gpt" or "mbr". These names can be customized by defining the following
+configuration options:
+
+::
+
+   CONFIG_FASTBOOT_GPT_NAME
+   CONFIG_FASTBOOT_MBR_NAME
+
+In Action
+---------
+
+Enter into fastboot by executing the fastboot command in U-Boot for either USB::
+
+   => fastboot usb 0
+
+or UDP::
+
+   => fastboot udp
+   link up on port 0, speed 100, full duplex
+   Using ethernet@4a100000 device
+   Listening for fastboot command on 192.168.0.102
+
+On the client side you can fetch the bootloader version for instance::
+
+   $ fastboot getvar version-bootloader
+   version-bootloader: U-Boot 2019.07-rc4-00240-g00c9f2a2ec
+   Finished. Total time: 0.005s
+
+or initiate a reboot::
+
+   $ fastboot reboot
+
+and once the client comes back, the board should reset.
+
+You can also specify a kernel image to boot. You have to either specify
+the an image in Android format *or* pass a binary kernel and let the
+fastboot client wrap the Android suite around it. On OMAP for instance you
+take zImage kernel and pass it to the fastboot client::
+
+   $ fastboot -b 0x80000000 -c "console=ttyO2 earlyprintk root=/dev/ram0 mem=128M" boot zImage
+   creating boot image...
+   creating boot image - 1847296 bytes
+   downloading 'boot.img'...
+   OKAY [  2.766s]
+   booting...
+   OKAY [ -0.000s]
+   finished. total time: 2.766s
+
+and on the U-Boot side you should see::
+
+   Starting download of 1847296 bytes
+   ........................................................
+   downloading of 1847296 bytes finished
+   Booting kernel..
+   ## Booting Android Image at 0x81000000 ...
+   Kernel load addr 0x80008000 size 1801 KiB
+   Kernel command line: console=ttyO2 earlyprintk root=/dev/ram0 mem=128M
+      Loading Kernel Image ... OK
+   OK
+
+   Starting kernel ...
+
+References
+----------
+
+.. [1] :doc:`fastboot-protocol`
+.. [2] https://developer.android.com/studio/releases/platform-tools