It should be possible to search the layer index for recipes that inherit a specific class.
All of the information required to support this is present, at least.
I've sent this for review, but currently we are waiting for a bunch of changes (most notably the Django 1.8 move covered in bug 9620) to go in and this will sit on top of those.
This is now implemented: https://layers.openembedded.org/layerindex/branch/master/recipes/?q=inherits%3Akernel Note the syntax is a little odd in that you could assume that searching is now keyword based since it does split out inherits:..., but it isn't - what's left over is still expected to match as a phrase.