sencha/bancha: use OpenTitan uart

The Sonata board support includes an OpenTitan uart driver; switch sencha
and bancha to use that (instead of the stopgap trivial uart).

Change-Id: Ibb2c150313ea5f2de90efddbc63a04e3ecd45409
diff --git a/sdk/boards/bancha.json b/sdk/boards/bancha.json
index 72678a3..7716a26 100644
--- a/sdk/boards/bancha.json
+++ b/sdk/boards/bancha.json
@@ -9,8 +9,8 @@
             "length" : 0x400000
         },
         "uart": {
-            "start": 0x54000000,
-            "end":   0x54000100
+            "start": 0x40000000,
+            "end":   0x40000100
         },
         "i2s": {
             "start": 0x54100000,
@@ -82,6 +82,12 @@
             "name": "MlTopFaultInterrupt",
             "number": 35,
             "priority": 3
+        },
+        {
+            "name": "UartRxWatermark",
+            "number": 2,
+            "priority": 3,
+            "edge_triggered": true
         }
     ],
     "defines" : [ "BANCHA" ],
diff --git a/sdk/boards/sencha.json b/sdk/boards/sencha.json
index 4c2d755..089fc17 100644
--- a/sdk/boards/sencha.json
+++ b/sdk/boards/sencha.json
@@ -81,6 +81,12 @@
             "name": "MailboxEInterrupt",
             "number": 32,
             "priority": 3
+        },
+        {
+            "name": "UartRxWatermark",
+            "number": 2,
+            "priority": 3,
+            "edge_triggered": true
         }
     ],
     "defines" : [ "SENCHA" ],
diff --git a/sdk/include/platform/sencha/platform-uart.hh b/sdk/include/platform/sencha/platform-uart.hh
new file mode 120000
index 0000000..1f6d864
--- /dev/null
+++ b/sdk/include/platform/sencha/platform-uart.hh
@@ -0,0 +1 @@
+../sunburst/platform-uart.hh
\ No newline at end of file