Do you have a picture of the mounting situation?
(to post pictures here: go to http://photoposting.is-great.net and follow instructions there)
The standard mounting strip of the glow steps doesn't need a lot of space (maybe 1 1/2 inches), but you will need to install/remove the steps every time you set up camp. But if the wood under your door is solid enough...?
Something like a Little Giant ladder might be a simpler solution.
I am sure others will chime in.
2014 Ford F350 XLT 6.2 SCLB + 2017 Northstar Arrow