1. An input/output (I/O) device comprising: a host interface; and a plurality of hardware resources coupled to the host interface; wherein the host interface includes a transaction layer packet (TLP) processing unit configured to receive and process a plurality of transaction layer packets sent by a plurality of processing units, each processing unit corresponding to a respective root complex; wherein the TLP processing unit is configured to identify a transaction type and a processing unit corresponding to each transaction layer packet and to store each transaction layer packet within a storage according to the transaction type and the processing unit; wherein the TLP processing unit is further configured to select from the storage one or more transaction layer packets for scheduling; and wherein the TLP processing unit is further configured to select and dispatch one or more transaction layer packets for processing by downstream application hardware.