Function fdt_first_subnode 

pub unsafe extern "C" fn fdt_first_subnode(
    fdt: *const c_void,
    offset: c_int,
) -> c_int

fdt_first_subnode() - get offset of first direct subnode @fdt: FDT blob @offset: Offset of node to check

returns: offset of first subnode, or -FDT_ERR_NOTFOUND if there is none