README: Include notes on reuse

This is just one way of doing it, but it shows the basic steps

README

@@ -19,7 +19,7 @@ Usage
 -----
 
 The makefiles are generally useable for your own projects with
-only minimal changes for the libopencm3 install path (See Installation)
+only minimal changes for the libopencm3 install path (See Reuse)
 
 For flashing the 'miniblink' example (after you built libopencm3 and the
 examples by typing 'make' at the top-level directory) onto the Olimex
@@ -43,3 +43,69 @@ You can also flash manually like this:
 Replace the "jtagkey-tiny.cfg" with whatever JTAG device you are using, and/or
 replace "stm32f1x.cfg" with your respective config file. Replace "foobar.hex"
 with the file name of the image you want to flash.
+
+Reuse
+-----
+
+If you want to use libopencm3 in your own project, this examples repository
+shows the general way.  (If there's interest, we can make a stub template
+repository)
+
+##### Create an empty repository
+
+    $ mkdir mycoolrobot && cd mycoolrobot && git init .
+
+##### Add libopencm3 as a submodule
+
+    $ git submodule add https://github.com/libopencm3/libopencm3
+
+##### Grab a copy of the basic rules
+These urls grab the latest from the libopencm3-examples repository
+
+    $ wget \
+    https://raw.githubusercontent.com/libopencm3/libopencm3-examples/master/examples/Makefile.rules \
+    -O libopencm3.rules.mk
+
+##### Grab a copy of your target Makefile
+in this case, for STM32L1
+
+    $ wget \
+    https://raw.githubusercontent.com/libopencm3/libopencm3-examples/master/examples/stm32/l1/Makefile.include \
+    -O libopencm3.target.mk
+
+##### Edit paths in libopencm3.target.mk
+Edit the _last_ line of libopencm3.target.mk and change the include to read
+include ../libopencm3.rules.mk (the amount of .. depends on where you put your
+project in the next step..
+
+##### beg/borrow/steal an example project
+For sanity's sake, use the same target as the makefile you grabbed up above)
+
+    $ cp -a \
+    somewhere/libopencm3-examples/examples/stm32/l1/stm32ldiscovery/miniblink \
+    myproject
+
+Add the path to OPENCM3_DIR, and modify the path to makefile include
+
+```
+$ diff -u
+---
+2014-01-24 21:10:52.687477831 +0000
++++ Makefile	2014-03-23 12:27:57.696088076 +0000
+@@ -19,7 +19,8 @@
+ 
+ BINARY = miniblink
+ 
++OPENCM3_DIR=../libopencm3
+ LDSCRIPT = $(OPENCM3_DIR)/lib/stm32/l1/stm32l15xxb.ld
+ 
+-include ../../Makefile.include
++include ../libopencm3.target.mk
+ 
+```
+
+You're done :)
+
+You need to run "make" inside the libopencm3 directory once to build the
+library, then you can just run make/make clean in your project directory as
+often as you like.