Android porting development kit could be obtained by
make pdk pdk_all
in your top repo dir. You can find the pdk doc in out/target/common/docs/online-pdk . If you open index.html directly you will find the css is all messed up. The quickest way might be moving the directory to /var/www, install one web server (I use thttpd) then open http://localhost/online-pdk/ .
The document is far from complete but it’s still a good reference to save a lot of time.