[media] Documentation: media: description of DMABUF importing in V4L2

This patch adds description and usage examples for importing
DMABUF file descriptor in V4L2.

Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
index a8cda1a..cd99436 100644
--- a/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-create-bufs.xml
@@ -6,7 +6,8 @@
 
   <refnamediv>
     <refname>VIDIOC_CREATE_BUFS</refname>
-    <refpurpose>Create buffers for Memory Mapped or User Pointer I/O</refpurpose>
+    <refpurpose>Create buffers for Memory Mapped or User Pointer or DMA Buffer
+    I/O</refpurpose>
   </refnamediv>
 
   <refsynopsisdiv>
@@ -55,11 +56,11 @@
     </note>
 
     <para>This ioctl is used to create buffers for <link linkend="mmap">memory
-mapped</link> or <link linkend="userp">user pointer</link>
-I/O. It can be used as an alternative or in addition to the
-<constant>VIDIOC_REQBUFS</constant> ioctl, when a tighter control over buffers
-is required. This ioctl can be called multiple times to create buffers of
-different sizes.</para>
+mapped</link> or <link linkend="userp">user pointer</link> or <link
+linkend="dmabuf">DMA buffer</link> I/O. It can be used as an alternative or in
+addition to the <constant>VIDIOC_REQBUFS</constant> ioctl, when a tighter
+control over buffers is required. This ioctl can be called multiple times to
+create buffers of different sizes.</para>
 
     <para>To allocate device buffers applications initialize relevant fields of
 the <structname>v4l2_create_buffers</structname> structure. They set the
@@ -109,7 +110,8 @@
 	    <entry>__u32</entry>
 	    <entry><structfield>memory</structfield></entry>
 	    <entry>Applications set this field to
-<constant>V4L2_MEMORY_MMAP</constant> or
+<constant>V4L2_MEMORY_MMAP</constant>,
+<constant>V4L2_MEMORY_DMABUF</constant> or
 <constant>V4L2_MEMORY_USERPTR</constant>. See <xref linkend="v4l2-memory"
 /></entry>
 	  </row>