*Bit-level* virtual serial port for Linux

Question

There are virtual serial port implementations for Linux but they all seem to be higher-level than the actual hardware reality of something like UART. What I'd like to do is to create a virtual serial port that is connected to a process that uses two single-bit channels for transmission and reception. The context of this is interactive testing of simulated circuitry, e.g. taking an FPGA configuration in Verilog that has a serial port, compiling it with Verilator into a native executable, and then communicating it through a virtual serial port.