Need Itinerary Suggestions for Spain/Porto

No, there isn't. The best transport options are to fly, to stay within Portugal, or to rent a car in Porto to drive north and circle back to return in Portugal.

The primary trains between Portugal and Spain are the once-daily overnight trains departing Lisbon and Coimbra and ending at either Madrid or San Sebastian. A couple of buses per day would cover the same routes and take all day or overnight. Train connections straight north from Porto to Santiago de Compostela are more fractured and slow than you'd expect, making driving more attractive.

Take the train from Porto via Vigo to Santiago de Compostela (2N) then on to Madrid (3N).
For your 6th night consider a stop in either Pontevedra or Leon.

Thanks for confirming what I thought:) I guess a flight out of Porto to Spain is the most efficient way to go.

That really depends on where in Spain you are looking at.

I really had my heart set on visiting northern Spain (San Sebastian, Basque country) or southern Spain with a beach added ( kids love water/ beach). I have done the Lisbon to Algarve, to Seville, then Granados to Madrid trip before (southern Spain). Thanks

Fly Porto to Pamplona (1N) via Madrid
Train to San Sebastián (3N)
Bus/train to Bilbao (2N)
Fly to Barcelona

I spent a good chunk of last summer in northern Spain. The temperature in the Basque Country is likely to be a lot milder than you'd have farther south. I think you'll appreciate that. Understand, though, that you could have some rain on any given day. The Basque Country is green for a reason.