docs/uzlib: Update description of decompress() and mention DecompIO.

docs/library/uzlib.rst

@@ -6,13 +6,33 @@
 
 |see_cpython_module| :mod:`python:zlib`.
 
-This modules allows to decompress binary data compressed with DEFLATE
-algorithm (commonly used in zlib library and gzip archiver). Compression
+This module allows to decompress binary data compressed with
+`DEFLATE algorithm <https://en.wikipedia.org/wiki/DEFLATE>`_
+(commonly used in zlib library and gzip archiver). Compression
 is not yet implemented.
 
 Functions
 ---------
 
-.. function:: decompress(data)
+.. function:: decompress(data, wbits=0, bufsize=0)
 
-   Return decompressed data as bytes.
+   Return decompressed *data* as bytes. *wbits* is DEFLATE dictionary window
+   size used during compression (8-15, the dictionary size is power of 2 of
+   that value). Additionally, if value is positive, *data* is assumed to be
+   zlib stream (with zlib header). Otherwise, if it's negative, it's assumed
+   to be raw DEFLATE stream. *bufsize* parameter is for compatibility with
+   CPython and is ignored.
+
+.. class:: DecompIO(stream, wbits=0)
+
+   Create a stream wrapper which allows transparent decompression of
+   compressed data in another *stream*. This allows to process compressed
+   streams with data larger than available heap size. In addition to
+   values described in :func:`decompress`, *wbits* may take values
+   24..31 (16 + 8..15), meaning that input stream has gzip header.
+
+   .. admonition:: Difference to CPython
+      :class: attention
+
+      This class is MicroPython extension. It's included on provisional
+      basis and may be changed considerably or removed in later versions.