交上 is a resultative verb formed by 交 ('to hand over') and 上 (resultative complement indicating upward completion). One sense is literally 'to hand in to a superior' (documents, reports). A second, metaphorical sense appears in fixed phrases like 交上好运 ('to have good luck') and 交上朋友 ('to make friends'). In both cases, 上 marks that the action has reached a successful endpoint.