Update README

README.md

@@ -1,2 +1,51 @@
 # extract-dtb
-Extract device tree blobs (dtb) from kernel images
+
+Tool to split a kernel image with appended dtbs into separated kernel and dtb files.
+
+A Device Tree is a data structure for describing hardware. They are used in a lot of
+ARM devices (e.g. Android), otherwise these would not be able to boot.
+
+This tool is similar to [split-appended-dtb](https://github.com/dianlujitao/split-appended-dtb)
+but it is written in Python and its code is simpler and almost 3x shorter.
+
+If you want to learn more about DTB you can have a look at the
+[Device Tree Reference](http://elinux.org/Device_Tree_Reference).
+
+## Usage
+
+```
+$ ./extract-dtb.py --help
+usage: extract-dtb.py [-h] [-n] filename
+
+Extract dtbs from kernel images.
+
+positional arguments:
+  filename    Android kernel image
+
+optional arguments:
+  -h, --help  show this help message and exit
+  -n          Do not extract, just output information
+```
+
+Example:
+
+```
+$ ./extract-dtb.py -n vmlinuz-motorola-titan
+Found 8 appended dtbs
+
+$ ./extract-dtb.py vmlinuz-motorola-titan
+Extracted 8 appended dtbs + kernel
+
+$ ls -l
+total 8808
+-rw-rw-r-- 1 pablo pablo  194829 jun 25 17:14 dtbdump_1.dtb
+-rw-rw-r-- 1 pablo pablo  194829 jun 25 17:14 dtbdump_2.dtb
+-rw-rw-r-- 1 pablo pablo  194829 jun 25 17:14 dtbdump_3.dtb
+-rw-rw-r-- 1 pablo pablo  194829 jun 25 17:14 dtbdump_4.dtb
+-rw-rw-r-- 1 pablo pablo  194829 jun 25 17:14 dtbdump_5.dtb
+-rw-rw-r-- 1 pablo pablo  192593 jun 25 17:14 dtbdump_6.dtb
+-rw-rw-r-- 1 pablo pablo  193324 jun 25 17:14 dtbdump_7.dtb
+-rw-rw-r-- 1 pablo pablo  193384 jun 25 17:14 dtbdump_8.dtb
+-rw-rw-r-- 1 pablo pablo 7368984 jun 25 17:14 kernel
+-rw-r--r-- 1 pablo pablo 9115814 jun 22 23:54 vmlinuz-motorola-titan
+```