In both of these two incidents of dreams and Joseph interpreting them, Joseph clearly states that he does not contain the ability to interpret the dreams in himself but it is God who gives the interpretation. In the prison he hypothetically asks the cupbearer, "Do not interpretations belong to God?" (Gen. 40:8) He is even more bold in his assertions to Pharaoh. In response to Pharaoh essentially asking him if he can interpret the dreams Joseph replies, "I cannot do it, but God will give Pharaoh the answer he desires." (Gen. 41:16) After hearing the dreams he begins his interpretation by saying, "God has revealed to Pharaoh what he is about to do." (Gen. 41:25, 28) After interpreting the dreams he states, "The reason the dream was given to Pharaoh in two forms is that the matter has been firmly decided by God, and God will do it soon." (Gen. 41:32)
Joseph's insistence that he is dependent on God for the interpretation not only reveals his maturity and good theology, but also leads to Pharaoh's recognition that the Spirit of God is on Joseph. (Gen. 41:38) Had Joseph taken the credit for his ability to interpret the dreams Pharaoh would have him instead of praising God... sort of. Pharaoh's declaration here of the Spirit being on Joseph is a confusing one for sure. Egypt being a polytheistic society it is doubtful that Pharaoh is here convinced that the God of the Hebrews is the one true God, denouncing the other pagan gods of his country. We shouldn't read too much into this text since the narrator doesn't go that far. This is likely nothing more than Pharaoh stating that Joseph is divinely enabled to interpret dreams.
This event closely resembles an event in the life of the prophet Daniel. During the exile in Babylon Daniel is called upon to interpret the dream of king Nebuchadnezzar. (Dan. 2) Similar to Joseph, Daniel is in a foreign country that does not fear God, Nebuchadnezzar's astrologers cannot interpret the dream, Daniel interprets the dream, Daniel tells the king that God has shown him what will happen in the future, Nebuchadnezzar acknowledges that God is with Daniel, and places him in a high position of authority in the kingdom. The similarities here are uncanny.