Split readme into small files

docs/flashing-usb.md

@@ -0,0 +1,33 @@
+We have two type of flashing
+1. Flash the image directly into USB. And boot using it.
+2. Copy the files into the USB drive. Then boot into initramfs. Then flash the image into the eMMC.
+
+## Flashing into eMMC
+1. `make release`
+2. Format the USB in vfat
+3. Copy out/[RELEASE].img.gz and out/board.itb to your usb drive's root
+4. Run
+```
+usb start
+usb tree
+fatls usb 0:1   # For fat
+ext4ls usb 0:1  # For ext4 if you insist
+fatload usb 0 0x80000000 board.itb
+
+setenv bootargs "console=ttyS0,115200 earlycon=uart8250,mmio,0x21c0500 root=/dev/ram0 rootwait rw"
+bootm 0x80000000
+```
+
+5. Inside initramfs, run
+```
+flash-emmc.sh
+```
+
+4. If it boots, create the A/B deployment scheme
+ - (WORK IN PROGRESS)
+
+## Flashing into USB
+On MacOS
+1. ./macos/flashusb.sh
+
+On Windows (Work In Progress)