Tokyo stocks opened mixed Wednesday, as selling of semiconductor-related issues following the fall of a key U.S. chip index was offset by buying of shares in Japanese companies that reported robust earnings the previous day. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 211.71 points, or 0.59 percent, from Tuesday to 35,948.95. The broader Topix index was up 3.02 points, or 0.12 percent, at 2,542.27. On the top-tier Prime Market, decliners were led by machinery and electric appliance issues, while transportation equipment and wholesale trade issues led gainers. At…