There seems to be quite a lot of wounds or cankers on the underneath of those branches that are covered with fungi.
We have an excellent fungi page here
All about fungi
Check out the links.
I would suggest pruning off the affected parts and disposing of the cuttings.
Also perhaps thinning the canopy out to let more light and air movement in may help.
There are a variety of fungicides on the market, if there's infestations still present after pruning or simply too many to prune off try applying some of the soluable spray ones.
I'm no expert in fungi, we dont have too many here. But it's not honey fungus. The old saying of improving the trees health and vigour is true ... make sure the trees not too deeply rooted, maybe have a ring of mulch instead of grass under the tree.