OS X tool for dumping and reconstructing the IOKit classes hierarchy. iokit-dumper directly generates DOT files (see here, which can then be processed with dot tool. Keep in mind this tool is in its early release, so stuff may happen. Also, careful when playing with the code, since a wrong read in the kernel will cause a kernel panic. Remember to always slide kernel addresses before reading from them.

https://github.com/jndok/iokit-dumper