Different from previous works, in this paper, we adopt D2D communication as a routing extension to traditional cellular uplinks thus enabling a two-hop route between a user and the serving BS via a D2D relay. Specifically, a BS establishes a cellular link with a mobile user only if the pilot signal strength received from the user is above a specified threshold; otherwise, the user may establish a D2D link with a neighboring user and connect to a nearby BS in a two-hop manner. We present a stochastic geometry based framework to analyze the coverage probability and average rate in such a two-hop multi-channel uplink cellular network where mobile users adopt the fractional channel inversion power control with maximum transmit power limit. As validated by extensive numerical results, the developed framework enables network designers to efficiently determine the optimal control parameters so as to achieve the optimum system performance. Our results show that employing D2D link based two-hop connection can significantly improve both the network coverage and average rate for uplink traffic.