Depends on whether you need flash programming only, debugging for H7 core only or debugging for both cores. In the first two cases there's almost nothing necessary, you could use e.g. http://openocd.zylin.com/#/c/4321/7/tcl/board/nucleo-h743zi.cfg and remove the QUADSPI stuff. Essentially this means 'source [find target/stm32h7x_dual_bank.cfg]' and set up the PLL and wait states if needed. In the last case ... I don't know.
