docs: ioctl: convert to ReST

Rename the iio documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

The cdrom.txt and hdio.txt have their own particular syntax.
In order to speedup the conversion, I used a small ancillary
perl script:

	my $d;
	$d .= $_ while(<>);
	$d =~ s/(\nCDROM\S+)\s+(\w[^\n]*)/$1\n\t$2\n/g;
	$d =~ s/(\nHDIO\S+)\s+(\w[^\n]*)/$1\n\t$2\n/g;
	$d =~ s/(\n\s*usage:)[\s\n]*(\w[^\n]*)/$1:\n\n\t  $2\n/g;
	$d =~ s/(\n\s*)(E\w+[\s\n]*\w[^\n]*)/$1- $2/g;
	$d =~ s/(\n\s*)(inputs|outputs|notes):\s*(\w[^\n]*)/$1$2:\n\t\t$3\n/g;
	print $d;

It basically add blank lines on a few interesting places. The
script is not perfect: still several things require manual work,
but it saved quite some time doing some obvious stuff.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/ioctl/botching-up-ioctls.txt → Documentation/ioctl/botching-up-ioctls.rst

+=================================
 (How to avoid) Botching up ioctls
 =================================
 

Documentation/ioctl/index.rst

+:orphan:
+
+======
+IOCTLs
+======
+
+.. toctree::
+   :maxdepth: 1
+
+   ioctl-number
+
+   botching-up-ioctls
+   ioctl-decoding
+
+   cdrom
+   hdio

Documentation/ioctl/ioctl-decoding.txt → Documentation/ioctl/ioctl-decoding.rst

+==============================
+Decoding an IOCTL Magic Number
+==============================
+
 To decode a hex IOCTL code:
 
 Most architectures use this generic format, but check
 include/ARCH/ioctl.h for specifics, e.g. powerpc
 uses 3 bits to encode read/write and 13 bits for size.
 
+ ====== ==================================
  bits   meaning
+ ====== ==================================
  31-30	00 - no parameters: uses _IO macro
 	10 - read: _IOR
 	01 - write: _IOW
@@ -16,9 +22,10 @@ uses 3 bits to encode read/write and 13 bits for size.
 	unique to each driver
 
  7-0	function #
+ ====== ==================================
 
 
 So for example 0x82187201 is a read with arg length of 0x218,
-character 'r' function 1. Grepping the source reveals this is:
+character 'r' function 1. Grepping the source reveals this is::
 
-#define VFAT_IOCTL_READDIR_BOTH         _IOR('r', 1, struct dirent [2])
+	#define VFAT_IOCTL_READDIR_BOTH         _IOR('r', 1, struct dirent [2])

drivers/gpu/drm/drm_ioctl.c

@@ -730,7 +730,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
  *     };
  *
  * Please make sure that you follow all the best practices from
- * ``Documentation/ioctl/botching-up-ioctls.txt``. Note that drm_ioctl()
+ * ``Documentation/ioctl/botching-up-ioctls.rst``. Note that drm_ioctl()
  * automatically zero-extends structures, hence make sure you can add more stuff
  * at the end, i.e. don't put a variable sized array there.
  *