doc: Document the new inline struct member kernel-doc style

We don't just need better doc toolchains, we also need better docs for
our doc toolchain!

v2: Make sure we don't have foo twice (Jani).

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/kernel-documentation.rst

@@ -484,7 +484,10 @@ span multiple lines. The continuation lines may contain indentation.
 In-line member documentation comments
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The structure members may also be documented in-line within the definition::
+The structure members may also be documented in-line within the definition.
+There are two styles, single-line comments where both the opening ``/**`` and
+closing ``*/`` are on the same line, and multi-line comments where they are each
+on a line of their own, like all other kernel-doc comments::
 
   /**
    * struct foo - Brief description.
@@ -502,6 +505,8 @@ The structure members may also be documented in-line within the definition::
          * Here, the member description may contain several paragraphs.
          */
         int baz;
+        /** @foobar: Single line description. */
+        int foobar;
   }
 
 Private members