docs/arm: add info on Raspberry Pi 3

Change-Id: Iee7bd2f99dfc11930a97683c2cf30c51110d6726
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5229
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

docs/develop/kernel/arch/arm/overview.rst

@@ -36,6 +36,7 @@ We have accumulated some notes and documentation on some of them.
    /kernel/arch/arm/ipaq
    /kernel/arch/arm/rpi1
    /kernel/arch/arm/rpi2
+   /kernel/arch/arm/rpi3
 
 TODO list
 ---------

docs/develop/kernel/arch/arm/rpi3.rst

@@ -0,0 +1,93 @@
+Raspberry Pi 3
+##############
+
+-  http://raspberrypi.org
+
+Hardware Information
+====================
+
+-  ARMv8 Architecture (64-bit)
+-  Broadcom BCM2837 (SoC)
+
+   -  Includes Quad ARM Cortex-A53 CPU @ 1.2 GHz
+   -  Includes VideoCore IV GPU
+
+-  SD Card Storage
+-  1 GB RAM
+-  Video Outputs
+
+   -  HDMI Video Output
+   -  Composite Video Output
+
+-  Ethernet
+-  Wifi b/g/n single band 2.4 GHz
+-  Bluetooth
+
+Setting up the Haiku SD card
+============================
+
+The Raspberry Pi SD card generally uses the MBR file system layout
+below. Partition 1 is all that is required to boot an OS.
+
+-  partition 1 – FAT32, bootable flag, type ‘c’
+-  partition 2 – BeFS, Haiku filesystem, type ‘eb’
+
+Boot Partition
+--------------
+
+Required Files
+~~~~~~~~~~~~~~
+
+-  bootcode.bin: 2nd stage bootloader
+-  start.elf: The GPU binary firmware image
+-  fixup.dat: Additional code for the GPU
+-  bcm2710-rpi-3-b.dtb: FDT binary for the Raspberry Pi 3B
+-  bcm2710-rpi-3-b-plus.dtb: FDT binary for the Raspberry Pi 3B+
+-  config.txt: A configuration file read by the Pi to start u-boot.bin
+-  u-boot.bin: u-boot loader for the Pi 3
+-  boot.scr: u-boot loader script for starting Haiku Loader
+-  uEnv.txt: configuration file for the boot.scr script
+-  haiku_loader.efi: Haiku Loader
+
+Optional Files
+~~~~~~~~~~~~~~
+
+-  vlls directory: Additional GPU code, e.g. extra codecs.
+-  uEnv.txt: u-boot configuration script to automate boot.
+
+Compiling Haiku and preparing SD card
+=====================================
+
+-  Create your ARM work directory
+   ``mkdir generated.arm; cd generated.arm``
+-  Build an ARM toolchain using
+   ``../configure --build-cross-tools arm ../../buildtools``
+-  Build SD card image using ``jam -q -j6 @minimum-mmc``
+-  Prepare customized SD card using the ``rune`` tool. E.g. ``rune -b rpi3 -i haiku-mmc.image /dev/mmcblk0``
+-  Ensure that partition 1 has partition type fat16: ``parted /dev/mmcblk0 set 1 esp off``
+
+Booting
+=======
+
+1. SOC finds bootcode.bin
+2. bootcode.bin runs start.elf
+3. start.elf reads config.txt and start u-boot
+4. u-boot.bin starts the Haiku loader
+5. Haiku loader boots Haiku kernel
+
+config.txt Options
+------------------
+
+::
+
+   uart_2ndstage=1
+   enable_uart=1
+   kernel=u-boot.bin
+
+
+Additional Information
+======================
+
+-  `Latest Raspberry Pi
+   firmware <http://github.com/raspberrypi/firmware/tree/master/boot>`__
+-  `config.txt options <http://www.elinux.org/RPiconfig>`__