Automatic reservation of backordered lines upon receipt of materials into warehouse

Hi.

We are using auto reservation feature to reserve materials automatically within the reservation time fence.

In case of quantity shortage, order line gets shipped partially and balance quantity get back ordered. When the warehouse receives the material into stock, how can we make sure the backordered line gets priority and reserved automatically?. we don't want to change the shipment priority manually for those backordered lines. Looking for automatic option to get allocated as soon as the stock is booked in the inventory.

This is not back-to-back  or ATO case.  the PO or WIP is not linked to the sale order line. We receive as general stock, but backordered lines to get higher piority than normal.