chore: snapshot before shared RS485 bus integration

components/hmi_link/include/hmi_link.h

@@ -0,0 +1,26 @@
+#ifndef HMI_LINK_H
+#define HMI_LINK_H
+
+#include "esp_err.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Start the local HMI UART link.
+ *
+ * Default pins:
+ *   EVSE GPIO22 = TX -> LCD RX
+ *   EVSE GPIO21 = RX <- LCD TX
+ *   Baudrate    = 115200 8N1
+ *
+ * The link uses one JSON object per line ('\n').
+ */
+esp_err_t hmi_link_init(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // HMI_LINK_H