kernel-dev: Updated phrasing for what a "defconfig" file is.

It was over simplistic.

(From yocto-docs rev: 8c66db6f2a35e9e57423690976a16d6a815ccbc9)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/kernel-dev/kernel-dev-common.xml

@@ -1603,8 +1603,11 @@
             <title>Creating a&nbsp;&nbsp;<filename>defconfig</filename> File</title>
 
             <para>
-                A <filename>defconfig</filename> file is simply a
-                <filename>.config</filename> renamed to "defconfig".
+                A <filename>defconfig</filename> file in the context of
+                the Yocto Project is often a <filename>.config</filename>
+                file that is copied from a build or a
+                <filename>defconfig</filename> taken from the kernel tree
+                and moved into recipe space.
                 You can use a <filename>defconfig</filename> file
                 to retain a known set of kernel configurations from which the
                 OpenEmbedded build system can draw to create the final