docs: Clean up and organize the admin guide a bit

The admin guide is a good start, but it's time to turn it into something
better than an unordered blob of files.  This is a first step in that
direction.  The TOC has been split up and annotated, the guides have been
reordered, and minor tweaks have been applied to a few of them.

One consequence of splitting up the TOC is that we don't really want to use
:numbered: anymore, since the count resets every time and there doesn't
seem to be a way to change that.  Eventually we probably want to group the
documents into sub-books, at which point we can go back to a single TOC,
but it's probably early to do that.

Reviewed-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/index.rst

-Linux Kernel User's Documentation
-=================================
+The Linux kernel user's and administrator's guide
+=================================================
 
-Contents:
+The following is a collection of user-oriented documents that have been
+added to the kernel over time.  There is, as yet, little overall order or
+organization here — this material was not written to be a single, coherent
+document!  With luck things will improve quickly over time.
+
+This initial section contains overall information, including the README
+file describing the kernel as a whole, documentation on kernel parameters,
+etc. 
 
 .. toctree::
-   :maxdepth: 2
-   :numbered:
+   :maxdepth: 1
 
    README
+   kernel-parameters
+   devices
+
+Here is a set of documents aimed at users who are trying to track down
+problems and bugs in particular.
+
+.. toctree::
+   :maxdepth: 1
+   
    reporting-bugs
+   security-bugs
    bug-hunting
    oops-tracing
    ramoops
-   initrd
-   init
    dynamic-debug-howto
-   security-bugs
-   kernel-parameters
+   init
+
+This is the beginning of a section with information of interest to
+application developers.  Documents covering various aspects of the kernel
+ABI will be found here.
+
+.. toctree::
+   :maxdepth: 1
+   
+   sysfs-rules
+
+The rest of this manual consists of various unordered guides on how to
+configure specific aspects of kernel behavior to your liking.
+
+.. toctree::
+   :maxdepth: 1
+   
+   initrd
    serial-console
    braille-console
    parport
@@ -25,8 +55,6 @@ Contents:
    sysrq
    unicode
    vga-softcursor
-   sysfs-rules
-   devices
    binfmt-misc
    mono
    java

Documentation/admin-guide/kernel-parameters.rst

-Kernel Parameters
-~~~~~~~~~~~~~~~~~
+The kernel's command-line parameters
+====================================
 
 The following is a consolidated list of the kernel parameters as
 implemented by the __setup(), core_param() and module_param() macros

Documentation/admin-guide/sysfs-rules.rst

-Rules on how to access information in the Linux kernel sysfs
-============================================================
+Rules on how to access information in sysfs
+===========================================
 
 The kernel-exported sysfs exports internal kernel implementation details
 and depends on internal kernel structures and layout. It is agreed upon

Documentation/admin-guide/vga-softcursor.rst

@@ -50,8 +50,8 @@ third parameter
 
 .. [#f1] see ``#define TRIDENT_GLITCH`` in ``drivers/video/vgacon.c``.
 
-Examples:
-=========
+Examples
+--------
 
 To get normal blinking underline, use::