A single document may appear as the child of multiple directories, so it doesn't inherently know who its parent is. That is, documents don't have a strong notion of path. You can easily traverse a tree of documents from parent to child, but not from child to parent.
The external storage does include a "parent" feature that is based on the stack of folders. You can do something similar in your app.
If you are looking for a way to get the parent folder of the folder the user chose then it is not possible.