schemas: legacy: extract (Up|Down)streamPort

This allows to remove some properties from 'Aggregate' schema which are
no longer needed, since there is now a more specific schema to use.

The defined schemas link to the design document [1], providing
background for easier configuration.

Tested: Schema Validator Pass

References:
[1] https://github.com/openbmc/docs/blob/master/designs/physical-topology.md

Change-Id: Iae5995f798d0cdce5dacb0bfd1ad1de6c542d2d8
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/schemas/global.json b/schemas/global.json
index c69b5a4..8504c7e 100644
--- a/schemas/global.json
+++ b/schemas/global.json
@@ -88,6 +88,12 @@
                             "$ref": "legacy.json#/$defs/ExternalSensor"
                         },
                         {
+                            "$ref": "legacy.json#/$defs/Port"
+                        },
+                        {
+                            "$ref": "legacy.json#/$defs/DownstreamPort"
+                        },
+                        {
                             "$ref": "virtual_sensor.json#/$defs/VirtualSensor"
                         },
                         {