Penthouse view for Doc: Now that Doc Rivers will be in Boston for the foreseeable future – he signed a five-year, $35 million contract back in May – the Celts coach needs a nice place to crash. Well, he’s found one. Rivers, who previously rented at the Mandarin Oriental Hotel, has purchased a penthouse at the Four Seasons Hotel. The well-compensated coach just closed on his new pad, paying $2.2 million for the 2-bed, 2.5-bath spread. Located on the 16th floor of the Boylston Street hotel, the penthouse has 1,801 square feet of living space, including enormous picture windows that look out over the Public Garden and Beacon Hill. It also offers 24-hour valet and concierge service. “He did his homework,’’ said realtor Beth Dickerson, who handled the sale. “He wanted to clearly understand the market, and at the end of the day, he liked the service and privacy of this property.’’ Rivers and his wife, Kristen, also own a place in exclusive Winter Park, Fla., and have four children. Their youngest, Spencer, is still in high school. Another son, Austin, just graduated and will play basketball for Duke this season.