This diff adds clk_get_by_ofw_node_index, which is like clk_get_by_ofw_index but operates on a specific OF node instead of the passed in device's OF node.
I'm using this in my Allwinner A64 branch for a clock node that looks like this:
bus_gates { #clock-cells = <1>; compatible = "allwinner,sunxi-multi-bus-gates-clk"; ... ahb1_parent { clocks = <&ahb1>; ... } ahb2_parent { clocks = <&ahb2>; ... } }