fdt_offset_ptr
tagp = fdt_offset_ptr(fdt, offset, FDT_TAGSIZE);
p = fdt_offset_ptr(fdt, offset++, 1);
lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
if (!fdt_offset_ptr(fdt, startoffset, offset - startoffset))
const void *fdt_offset_ptr(const void *fdt, int offset, unsigned int checklen);
return (void *)(uintptr_t)fdt_offset_ptr(fdt, offset, checklen);