It's quite common in older trees and there is no treatment. All trees make hundreds of fungal associations in the soil called mycorrhizae. These help the tree to gain nutrients, avoid other bacterial pathogens and communicate with it's neighbours. Only when the tree is old and weakened may fungi take hold and contribute to the death of the tree. I doubt yours is that advanced and the bracket fungi you can see is not that bad in comparison to honey fungus.
I'd just avoid disturbing the soil around your tree by excess digging or paving.