How to give permission for a role for editing help text for fields of custom types? I want role "RoleFoo" to have only the permission to edit the Help Text of all fields of  specific content types (contentypefoo1 and contentypefoo2).

How to do this?
The Field help helper module seems to be a good fit for this. some more details about it (from its project page, which is also here the image originates from):

The Field help helper module adds a link to entity configurable fields so that users with the appropriate permissions may easily edit the help text and label for a field in context of where the field displays.
Once a user's role is given the Edit field help text permission any user with that permission will be able to edit the help text or label of a configurable field without having access to administer fields.


Extra bonus: comes wth an official release for both D7 and D8 ...