I've started on some basic documentation for LAVA at https://wiki.linaro.org/Platform/Validation/LAVA/Documentation
This is mostly aimed at those who are trying to set it up for themselves, or get started on development for it. However I'm also starting to cover example jobs, and will expand that section further to list the available actions and the parameters they can take. It's a wiki, so feel free to add to it, or let me know if there's a particular section you have questions about and want to see expanded sooner.
Thanks,
Paul Larson