I found this figure in JSON spec
http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
They are usually called railroad diagrams, and they are basically a way of presenting a finite state automaton's transition diagram in a readable fashion. It is straight-forward to convert any regular expression into this format, but some regular expressions are tidier than others.
There are variations which work for context-free languages, so you will also find railroad diagrams for push-down automata. It is common that some high level of the grammar (for example, the non-terminal statement
) can be expressed as a regular expression of lower-level components (such as expression
).