/**
@defgroup    bootloader_riotboot_serial riotboot serial bootloader
@ingroup     bootloaders

# Overview
`riotboot_serial` is a variation on @ref bootloader_riotboot that adds the capability to flash
a new firmware using a serial (UART) connection.

After reset, riotboot will wait for `RIOTBOOT_DELAY_MS` ms, if within that time no command is
received it will automatically start the application.

If it reads the `B` character, it will enter bootloader mode where flash sectors can be erased
and written.

The application in `dist/tools/riotboot_serial` is used to talk to the bootloader and to flash
`.hex` files using the bootloader's serial protocol.

# Flashing a device
To flash a device that is equipped with the riotboot serial bootloader, set the `PROGRAMMER` variable
to `riotboot_serial` and chose the `PORT` accordingly.

e.g.

    make BOARD=same54-xpro PORT=/dev/ttyACM0 PROGRAMMER=riotboot_serial flash

*/