Stub

You can empty an Component Hierarchy as stub:

class SubSysModule extends Component {
   val io = new Bundle {
     val dx = slave(Stream(Bits(32 bits)))
     val dy = master(Stream(Bits(32 bits)))
   }
   io.dy <-< io.dx
}
class TopLevel extends Component {
   val dut = new SubSysModule().stub   //instance an SubSysModule as empty stub
}

It will generate the following Verilog code for example:

module SubSysModule (
  input               io_dx_valid,
  output              io_dx_ready,
  input      [31:0]   io_dx_payload,
  output              io_dy_valid,
  input               io_dy_ready,
  output     [31:0]   io_dy_payload,
  input               clk,
  input               reset
);


  assign io_dx_ready = 1'b0;
  assign io_dy_valid = 1'b0;
  assign io_dy_payload = 32'h0;

endmodule

You can also empty the top Component

SpinalVerilog(new Pinsec(500 MHz).stub)

What does stub do ?

first walk all the components and find out clock, then keep clock
then remove all children component
then remove all assignment and logic we dont want
tile 0 to output port