doc: Convert mainpage to Markdown

Convert to markdown. Our other GitHub files are in markdown
and doxygen natively supports it, so begin converting the
documentation entirely to markdown to minimize the number
of formats we have to comprehend.

Also rename it to index.md to match the other top level
files. Index and mainpage are interchangeable terms in
Doxygen.

Change-Id: I0f7274b47de6411f8d2d09d987fd1344e01a3986
Signed-off-by: Ben Walker <benjamin.walker@intel.com>

doc/Doxyfile

@@ -759,7 +759,7 @@ WARN_LOGFILE           =
 # Note: If this tag is empty the current directory is searched.
 
 INPUT                  = ../include/spdk \
-                         mainpage.txt \
+                         index.md \
                          directory_structure.txt \
                          ioat/index.txt \
                          nvme/index.txt \

doc/index.md

@@ -0,0 +1,23 @@
+# Storage Performance Development Kit {#index}
+
+# Introduction {#intro}
+
+- [SPDK on GitHub](https://github.com/spdk/spdk/)
+- [SPDK.io](http://www.spdk.io/)
+
+The Storage Performance Development Kit (SPDK) provides a set of tools and libraries
+for writing high performance, scalable, user-mode storage applications.
+It achieves high performance by moving all of the necessary drivers
+into userspace and operating in a polled mode instead of relying on interrupts,
+which avoids kernel context switches and eliminates interrupt handling overhead.
+
+## General Information {#general}
+
+ - \ref directory_structure
+
+## Modules {#modules}
+
+- \ref nvme
+- \ref nvmf
+- \ref ioat
+- \ref iscsi

doc/mainpage.txt

@@ -1,60 +0,0 @@
-/*-
- *   BSD LICENSE
- *
- *   Copyright (c) Intel Corporation.
- *   All rights reserved.
- *
- *   Redistribution and use in source and binary forms, with or without
- *   modification, are permitted provided that the following conditions
- *   are met:
- *
- *     * Redistributions of source code must retain the above copyright
- *       notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in
- *       the documentation and/or other materials provided with the
- *       distribution.
- *     * Neither the name of Intel Corporation nor the names of its
- *       contributors may be used to endorse or promote products derived
- *       from this software without specific prior written permission.
- *
- *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-/*!
-
-\mainpage SPDK Documentation
-
-\section intro Storage Performance Development Kit
-
-- <a href="https://github.com/spdk/spdk">SPDK on GitHub</a>
-- <a href="http://www.spdk.io/">SPDK.io</a>
-
-The Storage Performance Development Kit (SPDK) provides a set of tools and libraries
-for writing high performance, scalable, user-mode storage applications.
-It achieves high performance by moving all of the necessary drivers
-into userspace and operating in a polled mode instead of relying on interrupts,
-which avoids kernel context switches and eliminates interrupt handling overhead.
-
-\section general General Information
-
- - \ref directory_structure
-
-\section modules Modules
-
-- \ref nvme
-- \ref nvmf
-- \ref ioat
-- \ref iscsi
-
-*/