update Documentation/md.txt

@@ -2,6 +2,8 @@ Tools that manage md devices can be foun
    http://www.<country>.kernel.org/pub/linux/utils/raid/....
 
 
+Boot time assembly of RAID arrays
+---------------------------------
 
 You can boot with your md device with the following kernel command
 lines:

@@ -11,6 +13,8 @@ for old raid arrays without persistent s
 
 for raid arrays with persistent superblocks
   md=<md device no.>,dev0,dev1,...,devn
+or, to assemble a partitionable array:
+  md=d<md device no.>,dev0,dev1,...,devn
   
 md device no. = the number of the md device ... 
               0 means md0, 

@@ -34,7 +38,22 @@ A possible loadlin line (Harald Hoyer <H
 
 e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro
 
--------------------------------
+
+Boot time autodetection of RAID arrays
+--------------------------------------
+
+When md is compiled into the kernel (not as module), partitions of
+type 0xfd are scanned and automatically assembled into RAID arrays.
+This autodetection may be suppressed with the kernel parameter
+"raid=noautodetect".
+
+The kernel parameter "raid=partitionable" (or "raid=part") means
+that all auto-detected arrays are assembled as partitionable.
+
+
+Superblock formats
+------------------
+
 The md driver can support a variety of different superblock formats.
 (It doesn't yet, but it can)
 

@@ -82,7 +101,7 @@ array using HOT_REMOVE_DISK.
 
 
 Specific Rules that apply to format-0 super block arrays, and
-       arrays with no superblock (non-presistant).
+       arrays with no superblock (non-persistant).
 -------------------------------------------------------------
 
 An array can be 'created' by describing the array (level, chunksize