How to get ir.ExternKernel instance to initialize inductor Scheduler?

From the “_init_” method of Scheduler class in _inductor/, we see that the input nodes could be ir.ComputedBuffer, ir.TemplateBuffer or ir.ExternKernel instance list, but how can we construct a module to generate ir.ExternKernel instance to initialize the Scheduler?

The operator via make_fallback in torch/_inductor/ will produce ExternKernel ( ir.FallbackKernel ), instance, such as torch.fmax.
And convolution operator will produce ExternKernel, such as F.conv2d.