doc: design: clarifications to "FLASH MAP" section
Distinguish between flash areas and flash area IDs. Say what the
bootloader area is, since that's not discussed anywhere else.
@@ -110,13 +110,16 @@ region of disk with the following properties:
(1) An area can be fully erased without affecting any other areas.
(2) A write to one area does not restrict writes to other areas.
-The boot loader uses the following flash areas:
+The boot loader uses the following flash area IDs:
#define FLASH_AREA_BOOTLOADER 0
#define FLASH_AREA_IMAGE_0 1
#define FLASH_AREA_IMAGE_1 2
#define FLASH_AREA_IMAGE_SCRATCH 3
+The bootloader area contains the bootloader image itself. The other areas are
+described in subsequent sections.
+
*** IMAGE SLOTS
A portion of the flash memory is partitioned into two image slots: a primary
