Inner workings of System.IO.Ports.SerialPort

Could somebody provide me with information or links on sources, books on how the System.IO.Ports.SerialPort Object is working in detail. In specific, I would like to understand what the BaseStream Object does, what it's differences are compared to ReadByte or Write Method on SerialPort. What kind of Input Buffer we are talking about when it says SerialPort.ReadByte reads from the Input Buffer and so on.

In short:
How does the bits and bytes come down from the SerialPort to the UART and what happens in between?

I know the MSDN resources on the object. What I'm looking for is for a deeper insight in how I am able to take as much control as possible over when and how bytes are taken or put on the wire.

Best regards
AMT_VDM