Hello, that looks like three separate things.

The barnacle like growth is likely a fungus that is associated with wood decay I believe.  You should have the tree inspected by an arborist as it may be a hazard.

The branch with exposed wood looks like it has been wounded in the past.  I would suggest pruning this branch off the tree.

The final picture of the tree with white spots. Those are crustose lichens that grow commonly on bark of trees. They do not parasitize the tree or kill the bark. They are just growing on the surface and generally have not detrimental impact on the tree.

We have seen lots of general issues with trees this summer, including branch die and top dieback.  Although your trees may be in a unique situation, we generally think drought and heat have been having a big impact on tree health.