add new Installation guide

move the u-boot/serial stuff here from development, as the
reality of Liminix development in 2024 is that serial connection
is still the smoothest installation method

doc/development.rst

@@ -88,64 +88,6 @@ time with configurations for RP-PPPoE and/or Accel PPP.`
 Hardware devices
 ****************
 
-.. _serial:
-
-U-Boot and serial shenanigans
-=============================
-
-Every device that we have so far encountered in Liminix uses `U-Boot,
-the "Universal Boot Loader" <https://docs.u-boot.org/en/latest/>`_ so
-it's worth knowing a bit about it. "Universal" is in this context a
-bit of a misnomer, though: encountering *mainline* U-Boot is very rare
-and often you'll find it is a fork from some version last updated
-in 2008. Upgrading U-Boot is more or less complicated depending on the
-device and is outside scope for Liminix.
-
-To speak to U-Boot on your device you'll usually need a serial
-connection to it.  This is device-specific. Usually it involves
-opening the box, locating the serial header pins (TX, RX and GND) and
-connecting a USB TTL converter to them.
-
-The Rolls Royce of USB/UART cables is the `FTDI cable
-<https://cpc.farnell.com/ftdi/ttl-232r-rpi/cable-debug-ttl-232-usb-rpi/dp/SC12825?st=usb%20to%20uart%20cable>`_,
-but there are cheaper alternatives based on the PL2303 and CP2102 chipsets.  Or
-get creative and use the `UART GPIO pins <https://pinout.xyz/>`_ on a Raspberry Pi. Whatever you do, make sure
-that the voltages are compatible: if your device is 3.3V (this is
-typical but not universal), you don't want to be sending it 5v or
-(even worse) 12v.
-
-Run a terminal emulator such as Minicom on the computer at other end
-of the link. 115200 8N1 is the typical speed.
-
-.. NOTE::
-
-   TTL serial connections typically have no form of flow control and
-   so don't always like having massive chunks of text pasted into
-   them - and U-Boot may drop characters while it's busy. So don't
-   necessarily expect to copy-paste large chunks of text into the
-   terminal emulator and have it work just like that.
-
-   If using Minicom, you may find it helps to bring up the "Termimal
-   settings" dialog (C^A T), then configure "Newline tx delay" to
-   some small but non-zero value.
-
-When you turn the router on you should be greeted with some messages
-from U-Boot, followed by the instruction to hit some key to stop
-autoboot. Do this and you will get to the prompt. If you didn't see
-anything, the strong likelihood is that TX and RX are the wrong way
-around. If you see garbage, try a different speed.
-
-Interesting commands to try first in U-Boot are :command:`help` and
-:command:`printenv`.
-
-To do anything useful with U-Boot you will probably need a way to get
-large binary files onto the device, and the usual way to do this is by
-adding a network connection and using TFTP to download them. It's
-quite common that the device's U-Boot doesn't speak DHCP so it will
-need a static LAN address. You might also want to keep it away from
-your "real" LAN: see :ref:`bng` for some potentially useful tooling
-to use it on an isolated network.
-
 
 TFTP
 ====