How to use the tockloader.bootloader_serial.BootloaderSerial function in tockloader

Create an interactive terminal session with the board.

		This is a special-case use of Tockloader where this is really a helper
		function for running some sort of underlying terminal-like operation.
		Therefore, how we set this up is a little different from other
		tockloader commands. In particular, we do _not_ want `tockloader.open()`
		to have been called at this point.
		'''
		# By default, we use the serial connection and serial terminal. However,
		# tockloader supports other terminals, and we choose the correct one
		# here. There is no need to save the channel, since
		# `channel.run_terminal()` never returns.
		if self.args.rtt:
			channel = JLinkExe(self.args)
		else:
			channel = BootloaderSerial(self.args)
			channel.open_link_to_board(listen=True)

		channel.run_terminal()

For the bootloader, this means opening a serial port. For JTAG, not much
		needs to be done.
		'''

		# Verify both openocd and jlink are not set.
		if getattr(self.args, 'jlink', False) and getattr(self.args, 'openocd', False):
			raise TockLoaderException('Cannot use both --jlink and --openocd options')

		# Get an object that allows talking to the board.
		if hasattr(self.args, 'jlink') and self.args.jlink:
			self.channel = JLinkExe(self.args)
		elif hasattr(self.args, 'openocd') and self.args.openocd:
			self.channel = OpenOCD(self.args)
		else:
			self.channel = BootloaderSerial(self.args)

		# And make sure the channel is open (e.g. open a serial port).
		self.channel.open_link_to_board()