It's not really a variation. More like an error. The Q can't be dislodged without a lot of bother and White has no problem developing and more space.
Scotch Exchange

There is no 'obvious win'. Black will have problems finding an active continuation but his position is solid.
White could head for Q-side castling:
5...Ne7 6.Be3 (or Bf4) Nc6 7.Qd2, followed by Nc3 and O-O-O.

I have Shirov's first chessbase video on the Ruy Lopez and he spends around 45 minutes! talking about similar positions. I can't remember much but it was really instructive.
If you don't have chessbase you can download the 'chessbase reader' from the chessbase website. It works perfectly in linux wine too.
This variation of the scotch isn't even covered in many opening texts so apparently must be an obvious win for white, but I'm struggling to see how this is particularly advantageous for white.
Can anyone advise on how to take advantage of this position, general strategies, example games, suggested plans, traps etc etc? Any info linked to this line, the more info the better.
Thanks and best wishes