Solid is the new hardware device framework for KDE 4 that features, among other things, a hardware discovery layer which allows you to detect and use devices regardless of operating system or architecture. You can learn more about the Solid project at solid.kde.org.
For a more detailed (still not complete!) description, read here.
The API documentation can be found at api.kde.org
This tutorial is written for developers looking to use the Solid hardware discovery layer within their applications. It can also serve as a good starting point for developers looking to start working on the Solid framework.