diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 759e708dac..96755bd096 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -3409,9 +3409,14 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                 </para>
 
                 <para>
-                    The <link linkend='var-KERNEL_SRC'><filename>KERNEL_SRC</filename></link>
-                    variable is identical to the <filename>KERNEL_PATH</filename>
-                    variable.
+                    To help maximize compatibility with out-of-tree drivers
+                    used to build modules, the OpenEmbedded build system also
+                    recognizes and uses the
+                    <link linkend='var-KERNEL_SRC'><filename>KERNEL_SRC</filename></link>
+                    variable, which is identical to the
+                    <filename>KERNEL_PATH</filename> variable.
+                    Both variables are common variables used by external
+                    Makefiles to point to the kernel source directory.
                 </para>
             </glossdef>
         </glossentry>
@@ -3429,9 +3434,14 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
                 </para>
 
                 <para>
-                    The <link linkend='var-KERNEL_PATH'><filename>KERNEL_PATH</filename></link>
-                    variable is identical to the <filename>KERNEL_SRC</filename>
-                    variable.
+                    To help maximize compatibility with out-of-tree drivers
+                    used to build modules, the OpenEmbedded build system also
+                    recognizes and uses the
+                    <link linkend='var-KERNEL_PATH'><filename>KERNEL_PATH</filename></link>
+                    variable, which is identical to the
+                    <filename>KERNEL_SRC</filename> variable.
+                    Both variables are common variables used by external
+                    Makefiles to point to the kernel source directory.
                 </para>
             </glossdef>
         </glossentry>