Add info stub for SoC UART

sections/soc/soc.tex

@@ -87,7 +87,8 @@ The complete FPGA design consists not only of the CPU core, but a number of comp
 
 \subsection{UART}
 
-% TODO
+The easiest way to communicate with an embedded system is usually through a serial interface. To ensure the best compatibility with existing software, a National Semiconductor 16550 UART was reimplemented from scratch instead of creating a new design. Thus, the modules's functionality and design can be found in the 16550's datasheet.
+% TODO ref
 
 \subsection{DVI graphics}