Hi Sanju,
Well it depends on your requirements, i.e, if you require to use the RDK or the EZSDK (http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/717/t/166685.aspx)
For the EZSDK you can find the code here:
http://downloads.ti.com/dsps/dsps_public_sw/ezsdk/5_05_02_00/index_FDS.html
it also contains some pdfs like the developers guide which will give you an idea about how to use it.
Ridgerun also has a well documented SDK for the DM81xx devices, customers normally use it when they want to developed their application based on gstreamer, all the packages are already integrated in the SDK and it is autotools based (make config, make build, make install), it already handles the EZSDK too (you just need to download it from TI site). It is well documented with a getting started guide:
https://developer.ridgerun.com/wiki/index.php/Spectrum_Digital_DM8168_EVM
https://developer.ridgerun.com/wiki/index.php/Getting_Started_Guide_for_DM8168_EVM
https://developer.ridgerun.com/wiki/index.php/Gstreamer_pipelines_for_DM816x_and_DM814x
-David