HDP is one of the labels for an HDMI in. On the 3808 the 4 hdmi ins have the following labels: dvd, hdp, tv/cbl, dvr... as I said i always assumed that hdp was for High Def Player but who knows.
In the end it doesn't really matter, especially if you rename your inputs as I have done. (PS3, HD-DVD, xbox 360, ect.). However, I use the remote that came with the 3808 so I have to remember the relationship between the title and the input label. If you have a fancy remote I guess you wouldn't even have to do that.
