ieee802154 wpan radio protocol over USB

Overview
========

The document describes protocol between 802.15.4 physical radio and Linux
kernel driver over USB. Protocol is based on atusb Linux driver protocol
found inside Linux kernel: drivers/net/ieee802154/atusb.h

Packet structure
================

Command opcodes are inside bRequest field. bRequest and wIndex are one octet
long.

Commands from Host to Device
============================

	Opcode 0x00 - Reset		bRequest

		Reset the Radio

	Opcode 0x01 - Transmit		bRequest

		Sequence number:	wIndex

		Transmit data from Host to Device

	Opcode 0x02 - ED		bRequest

		TBD

	Opcode 0x03 - Set Channel	bRequest

		Set ieee802154 channel

		Page		1 octet
		Channel		1 octet

	Opcode 0x04 - Start		bRequest

		Start ieee802154 device

	Opcode 0x05 - Stop		bRequest

		Stop ieee802154 device

Add wpan radio protocol specification
wpanusb: Add wpan radio protocol specification

Change-Id: I4ab00d87de50a9efa5b715649d4b5154e37ce1c0
Signed-off-by: Andrei Emeltchenko <a6565233ddc88e4fb9c66c1d70743223493f2ed4@intel.com>
