In order to use these passes, AOV Output nodes need to be added to shaders.
For each node, a name can be assigned and a Color or Value input can be connected to it.
After adding a corresponding pass with the same name in the Render Pass settings, Cycles
will then render this pass, filling in the connected data for each shader that contains
a matching AOV output node.
In addition to that, there is also an option for baking a specified AOV pass.
Therefore, this patch depends on D3203.