Seems to be pretty much over now - poorly executed at a relatively low level (colonel level is the guess at present from US TV armchair experts). US former military officers calling Turkish mates at one-star level and above being told they have no idea WTF is going on or who started it.
When it came to it, and a tank seen on TV was surrounded by literally thousands of civilians, the co-ax gun was fired above their heads without effect rather than at them and then the tank crew accepted they weren't going anywhere.
There have been casualties, initially civilians on the Bosphorus Bridge as televised, and various reports of loud explosions either tank main armament or helicopter borne munitions near the Parliament building.