Offer Approval Workflow | How to set an AOR on Department reflecting on Department Tree

Hi team
our client asks to have a step of the job offer approval workflow so the approver has an area of responsibility based on a Department.
In detail, the client manages a department tree and expects the if the AOR is based on the "Department Father", the approver has to receive the request for approval including all the job offer with a "Department son"
Actually, this is not working: User with AOR based on Department Father is not receiving the request for the approval of a job offer with a department son.

Were I clear in my explanation?
Could you please guide me?