i2c: New bus driver for the TAOS evaluation modules

This is a new I2C bus driver for the TAOS evaluation modules. Developped
and tested on the TAOS TSL2550 EVM.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/i2c/busses/i2c-taos-evm

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+Kernel driver i2c-taos-evm
+
+Author: Jean Delvare <khali@linux-fr.org>
+
+This is a driver for the evaluation modules for TAOS I2C/SMBus chips.
+The modules include an SMBus master with limited capabilities, which can
+be controlled over the serial port. Virtually all evaluation modules
+are supported, but a few lines of code need to be added for each new
+module to instantiate the right I2C chip on the bus. Obviously, a driver
+for the chip in question is also needed.
+
+Currently supported devices are:
+
+* TAOS TSL2550 EVM
+
+For addtional information on TAOS products, please see
+  http://www.taosinc.com/
+
+
+Using this driver
+-----------------
+
+In order to use this driver, you'll need the serport driver, and the
+inputattach tool, which is part of the input-utils package. The following
+commands will tell the kernel that you have a TAOS EVM on the first
+serial port:
+
+# modprobe serport
+# inputattach --taos-evm /dev/ttyS0
+
+
+Technical details
+-----------------
+
+Only 4 SMBus transaction types are supported by the TAOS evaluation
+modules:
+* Receive Byte
+* Send Byte
+* Read Byte
+* Write Byte
+
+The communication protocol is text-based and pretty simple. It is
+described in a PDF document on the CD which comes with the evaluation
+module. The communication is rather slow, because the serial port has
+to operate at 1200 bps. However, I don't think this is a big concern in
+practice, as these modules are meant for evaluation and testing only.