doc: Convert Chromium OS docs to rst

Move this documentation over to reST. Move the example files into a files/
directory so they are still separate.

Do a few minor updates while we are here:
- Tidy up sandbox build instructions
- Update my github account name
- Add some talks and links

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/chromium/overview.rst b/doc/chromium/overview.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright 2020 Google LLC
+
+Chromium OS Support in U-Boot
+=============================
+
+Introduction
+------------
+
+This describes how to use U-Boot with Chromium OS. Several options are
+available:
+
+   - Running U-Boot from the 'altfw' feature, which is available on selected
+     Chromebooks from 2019 onwards (initially Grunt). Press '1' from the
+     developer-mode screen to get into U-Boot. See here for details:
+     https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_mode.md
+
+   - Running U-Boot from the disk partition. This involves signing U-Boot and
+     placing it on the disk, for booting as a 'kernel'. See
+     :doc:`chainload` for information on this. This is the only
+     option on non-U-Boot Chromebooks from 2013 to 2018 and is somewhat
+     more involved.
+
+   - Running U-Boot with Chromium OS verified boot. This allows U-Boot to be
+     used instead of either or both of depthcharge (a bootloader which forked
+     from U-Boot in 2013) and coreboot. See :doc:`run_vboot` for more
+     information on this.
+
+   - Running U-Boot from coreboot. This allows U-Boot to run on more devices
+     since many of them only support coreboot as the bootloader and have
+     no bare-metal support in U-Boot. For this, use the 'coreboot' target.
+
+   - Running U-Boot and booting into a Chrome OS image, but without verified
+     boot. This can be useful for testing.
+
+
+Talks and documents
+-------------------
+
+Here is some material relevant to Chromium OS verified boot with U-Boot:
+
+   - "U-Boot with Chrome OS and firmware packaging"
+
+     - Author: Simon Glass
+     - Presented at Open Source Firmware Conference 2018, Erlangen
+     - Describes the work in progress as at the end of 2018
+     - Slides at `OSFC <https://2018.osfc.io/uploads/talk/paper/26/U-Boot_with_Chrome_OS_and_firmware_packaging.pdf>`_
+     - Video on `Youtube <https://www.youtube.com/watch?v=1jknxUvmwpo>`_
+
+   - "Verified Boot in Chrome OS and how to make it work for you"
+
+     - Author: Simon Glass
+     - Presented at ELCE 2013, Edinburgh
+     - Describes the original 2013 implementation as shipped on snow (first
+       `ARM Chromebook was a Samsung Chromebook <https://www.cnet.com/products/samsung-series-3-chromebook-xe303c12-11-6-exynos-5250-2-gb-ram-16-gb-ssd-bilingual-english-french/>`_
+       with Samsung Exynos5250 `review <https://www.cnet.com/reviews/samsung-chromebook-series-3-review/>`_),
+       spring (`HP Chromebook 11 <https://www.cnet.com/products/hp-chromebook-11-g2-11-6-exynos-5250-4-gb-ram-16-gb-emmc/>`_)
+       and pit/pi (`Samsung Chromebook 2 <https://www.cnet.com/products/samsung-chromebook-2-xe503c12-11-6-exynos-5-octa-4-gb-ram-16-gb-ssd/>`_
+       with Exynos 5 Octa 5420 in 2014).
+     - Slides at `Google research <https://research.google/pubs/pub42038/>`_
+     - Video at `Youtube <https://www.youtube.com/watch?v=kdpZC9jFzZA>`_
+
+   - "Chrome University 2018: Chrome OS Firmware and Verified Boot 201"
+
+     - Author: Duncan Laurie
+     - Describes Chrome OS firmware as of 2018 and includes a wide range of
+       topics. This has no U-Boot information, but does cover coreboot and also
+       talks about the Chrome OS EC and Security chip. This is probably the
+       best introduction talk.
+     - Video at `YouTube <https://www.youtube.com/watch?v=WY2sWpuda2g>`_
+
+   - `Chromium OS U-Boot <https://www.chromium.org/developers/u-boot>`_
+
+   - `Firmware porting Guide <https://www.chromium.org/chromium-os/firmware-porting-guide>`_