soc: Add initial ESP32-C3 support

From internal commit 7761d6e8

components/soc/esp32c3/uart_periph.c

@@ -0,0 +1,37 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "soc/uart_periph.h"
+
+/*
+ Bunch of constants for every UART peripheral: GPIO signals, irqs, hw addr of registers etc
+*/
+const uart_signal_conn_t uart_periph_signal[SOC_UART_NUM] = {
+    {
+        .tx_sig = U0TXD_OUT_IDX,
+        .rx_sig = U0RXD_IN_IDX,
+        .rts_sig = U0RTS_OUT_IDX,
+        .cts_sig = U0CTS_IN_IDX,
+        .irq = ETS_UART0_INTR_SOURCE,
+        .module = PERIPH_UART0_MODULE,
+    },
+    {
+        .tx_sig = U1TXD_OUT_IDX,
+        .rx_sig = U1RXD_IN_IDX,
+        .rts_sig = U1RTS_OUT_IDX,
+        .cts_sig = U1CTS_IN_IDX,
+        .irq = ETS_UART1_INTR_SOURCE,
+        .module = PERIPH_UART1_MODULE,
+    }
+};