A driver and user land utility for the Sparkfun Serial Controlled Motor
Driver module as illustrated here:

https://www.sparkfun.com/products/13911

A SCMD module is a ARM SOC simular to a Arduino in front of a motor
driver chip. The single SCMD module can control two motors and up to
16 additional modules can be chained together using an internal I2C
bus. One can interface with the SCMD using tty uart commands, SPI or
I2C. The driver in this commit adds a kernel driver for the I2C and
SPI interfaces. The command line utility provides a set of
convenience commands that support most of the functions of the SCMD
and is able to use the tty uart mode, SPI user land or the included
kernel driver in a uniform manor.

The use of the SCMD module is mostly for small robots and the like,
but it can control anything that is controllable by voltage.