Coordinated boot synchronization and startup of information handling system subsystems

An information handling system may include a processor, a subsystem communicatively coupled to the processor, and a management controller communicatively coupled to the processor and the subsystem and configured for out-of-band management of the information handling system, the management controller further configured to, in response to an alternating current power cycle of the information handling system: cause a basic input/output system of the information handling system to pause its boot process prior to enumeration of functions of the subsystem; and upon completion of the boot process of the subsystem and initialization of virtual functions of the subsystem, cause the basic input/output system to unpause the boot process in order to enumerate the functions of the subsystem including the virtual functions.