Add skeletons

src/sub/downstream_path/downstream_path.sv

@@ -0,0 +1,17 @@
+module downstream_path (
+    input               clk,
+    input               rst,
+
+    taxi_axis_if.snk    s_axis_data,
+    taxi_axis_if.src    m_axis_data,
+
+    taxi_axi_if.rd_mst  m_axi_rd,
+    taxi_axi_if.wr_mst  m_axi_wr,
+    
+    taxi_apb_if.slv     s_apb_cfg,
+
+    output logic        o_irq_m2s,
+    output logic        o_irq_s2m
+);
+
+endmodule

src/sub/upstream_path/upstream_path.sv

@@ -0,0 +1,17 @@
+module upstream_path (
+    input               clk,
+    input               rst,
+
+    taxi_axis_if.snk    s_axis_data,
+    taxi_axis_if.src    m_axis_data,
+
+    taxi_axi_if.rd_mst  m_axi_rd,
+    taxi_axi_if.wr_mst  m_axi_wr,
+    
+    taxi_apb_if.slv     s_apb_cfg,
+
+    output logic        o_irq_m2s,
+    output logic        o_irq_s2m
+);
+
+endmodule