doc/dumping: Add info about naddump

doc/dumping

@@ -27,6 +27,22 @@ Technical details:
 
    mtd4 - rootfs.jffs2 (a fucking copy of the above rootfs?)
 
+For dumping mtd parition is used tool nanddump. Here is example how to dump
+kernel image without padding to file zImage:
+
+ $ nanddump -i -o -b -s 0x00000800 -l 0x001FF800 -f zImage /dev/mtd2
+
+Params means:
+-i - "Ignore errors"
+-o - "Omit oob data"
+-b - "Omit bad blocks"
+-s - "Start address"
+-l - "Length"
+-f - "Output file"
+
+Please note that some new versions of naddump have some options removed and
+some are enabled by default. Before using check params of your nanddump version.
+
 
 // Extra notes //