This was part of the old staking spec in https://github.com/cosmos/cosmos-sdk/blob/develop/docs/spec/staking/old/spec.md

We should have a high level spec module called fees that details how this is done (copy over and update the old spec for this). Note it seems like it shouldn't be part of staking. Fees are distributed according to staking information, but so is governance power, etc. Might help to keep them separate