White spots on my maple trees
This appears to be White spot lichen phylctis argena which is usually not harming your tree. This tends to grow on older trees and shrubs.
To my eye, this tree looks like it may need some pruning (not for the white spots but because of the dense systems of branches.
A certified arborist could advise you on pruning and the spots. https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional
Thank you for writing.