Techniques and mechanisms to provide common interface logic for multiple protocol engines to access physical layer circuitry at different times. In an embodiment, a state machine of an interface device is to participate in exchanges with physical layer resources on behalf of any of various protocol engines coupled to the interface device via different respective interfaces. Based on state transitions by the state machine, circuitry corresponding to a particular one of such interfaces may selectively send a clock signal for operation of a port controller attempting to access the physical layer circuitry. In some embodiments, multiple interface devices are configured to provide an hierarchical interface architecture for more than two port controllers that variously support at least two protocols.