diff --git a/Documentation/mn10300/compartmentalisation.txt b/Documentation/mn10300/compartmentalisation.txt
new file mode 100644
index 0000000..8958b51
--- /dev/null
+++ b/Documentation/mn10300/compartmentalisation.txt
@@ -0,0 +1,60 @@
+		   =========================================
+		   PART-SPECIFIC SOURCE COMPARTMENTALISATION
+		   =========================================
+
+The sources for various parts are compartmentalised at two different levels:
+
+ (1) Processor level
+
+     The "processor level" is a CPU core plus the other on-silicon
+     peripherals.
+
+     Processor-specific header files are divided among directories in a similar
+     way to the CPU level:
+
+	(*) include/asm-mn10300/proc-mn103e010/
+
+	    Support for the AM33v2 CPU core.
+
+     The appropriate processor is selected by a CONFIG_MN10300_PROC_YYYY option
+     from the "Processor support" choice menu in the arch/mn10300/Kconfig file.
+
+
+ (2) Unit level
+
+     The "unit level" is a processor plus all the external peripherals
+     controlled by that processor.
+
+     Unit-specific header files are divided among directories in a similar way
+     to the CPU level; not only that, but specific sources may also be
+     segregated into separate directories under the arch directory:
+
+	(*) include/asm-mn10300/unit-asb2303/
+	(*) arch/mn10300/unit-asb2303/
+
+	    Support for the ASB2303 board with an ASB2308 daughter board.
+
+	(*) include/asm-mn10300/unit-asb2305/
+	(*) arch/mn10300/unit-asb2305/
+
+	    Support for the ASB2305 board.
+
+     The appropriate processor is selected by a CONFIG_MN10300_UNIT_ZZZZ option
+     from the "Unit type" choice menu in the arch/mn10300/Kconfig file.
+
+
+============
+COMPILE TIME
+============
+
+When the kernel is compiled, symbolic links will be made in the asm header file
+directory for this arch:
+
+	include/asm-mn10300/proc => include/asm-mn10300/proc-YYYY/
+	include/asm-mn10300/unit => include/asm-mn10300/unit-ZZZZ/
+
+So that the header files contained in those directories can be accessed without
+lots of #ifdef-age.
+
+The appropriate arch/mn10300/unit-ZZZZ directory will also be entered by the
+compilation process; all other unit-specific directories will be ignored.