add documentation for FileLike, the base class and its methods such as readline
diff --git a/documentation/pyserial_api.rst b/documentation/pyserial_api.rst
index 82024f1..70929da 100644
--- a/documentation/pyserial_api.rst
+++ b/documentation/pyserial_api.rst
@@ -210,6 +210,71 @@
Set software flow control state.
+.. class:: FileLike
+
+ .. method:: readline()
+
+ An abstract file like class. It is used as base class for :class:`Serial`.
+
+ This class implements readline and readlines based on read and
+ writelines based on write.
+ This class is used to provide the above functions for to Serial
+ port objects.
+
+ Note that when the serial port was opened with _NO_ timeout that
+ readline blocks until it sees a newline (or the specified size is
+ reached) and that readlines would never return and therefore
+ refuses to work (it raises an exception in this case)!
+
+ .. method:: readline(size=None, eol='\n')
+
+ :param size: Max number of bytes to read, ``None`` -> no limit.
+ :param eol: The end of line character.
+
+ Read a line which is terminated with end-of-line (eol) character
+ ('\n' by default) or until timeout.
+
+ .. method:: readlines(sizehint=None, eol='\n')
+
+ :param size: Ignored parameter.
+ :param eol: The end of line character.
+
+ Read a list of lines, until timeout. ``sizehint`` is ignored and only
+ present for API compatibility with built-in File objects.
+
+ .. method:: xreadlines(sizehint=None)
+
+ Just calls ``readlines`` - here for compatibility.
+
+ .. method:: writelines(sequence)
+
+ Write a list of strings to the port.
+
+ .. method:: flush()
+
+ Flush of file like objects. It's a no-op in this class, may be overridden.
+
+ .. method:: read()
+
+ Raises NotImplementedError, needs to be overridden by subclass.
+
+ .. method:: write()
+
+ Raises NotImplementedError, needs to be overridden by subclass.
+
+
+ To be able to use the file like object as iterator for e.g.
+ ``for line in Serial(0): ...`` usage:
+
+ .. method:: next()
+
+ Return the next line by calling :meth:`readline`.
+
+ .. method:: __iter__()
+
+ Returns self.
+
+
Exceptions
==========
@@ -245,3 +310,8 @@
.. data:: SIXBITS
.. data:: SEVENBITS
.. data:: EIGHTBITS
+
+Others
+-------
+.. data:: XON
+.. data:: XOFF