As Igor mentioned, we don't have an RCS 308 here to test with. We have 2 ways to add support for new device drivers. Either way, the developer uses the Pluto Admin site and chooses "Advanced, device templates", and then adds the device, the data it needs, the commands it implements, and the events it fires.
Then there are 2 choices: Run DCEGen, which will create a C++ project with member functions, and stubs for the commands. That means the developer needs to know C++, but virtually anything can be done with teh driver. More info is in the programmer's guide: http://plutohome.com/support/index.php?section=document&docID=15
and in the DCE programmer's guide, including a tutorial: http://plutohome.com/support/index.php?section=document&docID=51
We also have a new 'lite' program called Generic Serial Driver that for most simple serial i/o devices works with a 'point-and-click' interface using the I/R codes page in the Pluto Admin site. It includes an embedded Ruby engine, so some basic coding is possible too. This driver should be included in the 184.108.40.206 build, and will be documented then.