Add a short main page to doxygen docu

Author: manorom

clang/tools/sotoc/Doxyfile

@@ -733,7 +733,7 @@ WARN_LOGFILE           =
 # spaces.
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = src
+INPUT                  = docs/main.md src
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -869,7 +869,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE =
+USE_MDFILE_AS_MAINPAGE = docs/main.md
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing

clang/tools/sotoc/docs/main.md

@@ -0,0 +1,19 @@
+sotoc - Source Transformation for OpenMP Code (suggestions for a better name are greatly appreciated) {#mainpage}
+=====================================================================================================
+
+`sotoc` is written as a Clang tool and makes use of the Clang tooling
+infrastructure to parse C source files, search for target regions and other
+code that will be offloaded to a target device, and then extract and transform
+this code into new C code that can then be compiled by a target compiler into
+a target image to be used as a OpenMP device binary.
+The tool is part of this Clang repository and is automatically build together
+with clang.
+
+The tool comes with a regression test suite that uses `llvm-lit`.
+The tests can be run using the CMake generated build script when the CMake
+option `SOTOC_ENABLE_TESTS` is set to `ON` by running
+
+    $ make check-sotoc
+
+To run the tests, make sure that LLVM's `FileCheck` tool is in the path.
+