Replace serial.c of quantum/split_common/ (#4669)

* Add provisional Helix implementation to test the quantum/split_common.

* copy keyboards/helix/serial.[ch] to quantum/split_common/

* Make serial.c a pure driver.

Remove buffer name and buffer size from serial.c. They should be placed in the caller(matrix.c, split_utils.c).

* remove quantum/split_common/serial_backward_compatibility.h

* Changed array serial_master_buffer to structure serial_m2s_buffer.

* Changed array serial_slave_buffer to structure serial_s2m_buffer.

* Change keyboards/miniaxe/matrix.c

I also made changes to quantum/split_comon/matrix.c to keyboards/miniaxe/matrix.c.

Note: I contacted @ka2hiro, creator of miniaxe, and I got permission to change keyboards/miniaxe/matrix.c.

* update history comment in quantum/split_common/serial.c

* Revert "Add provisional Helix implementation to test the quantum/split_common."

This reverts commit 168c82ef82c88e79979d9796bab9cc819cc2f685.

* fix keyboards/miniaxe/matrix.c, quantum/split_common/matrix.c

avr-gcc 4.9.[23] report error.
avr-gcc 5.4.0, avr-gcc 7.3.0 pass.
It is funny.

* update comment quantum/split_common/serial.c

* Reserve RGBLIGHT_SPLIT macro in quantum/split_common

1 files changed, 31 insertions, 0 deletions

diff --git a/quantum/split_common/matrix.h b/quantum/split_common/matrix.h
new file mode 100644
index 000000000..b5cb45bae
--- /dev/null
+++ b/quantum/split_common/matrix.h
@@ -0,0 +1,31 @@
+#ifndef SPLIT_COMMON_MATRIX_H
+#define SPLIT_COMMON_MATRIX_H
+
+#include <common/matrix.h>
+
+#ifdef RGBLIGHT_ENABLE
+#   include "rgblight.h"
+#endif
+
+typedef struct _Serial_m2s_buffer_t {
+#ifdef BACKLIGHT_ENABLE
+    uint8_t backlight_level;
+#endif
+#if defined(RGBLIGHT_ENABLE) && defined(RGBLIGHT_SPLIT)
+    rgblight_config_t rgblight_config; //not yet use
+    //
+    // When MCUs on both sides drive their respective RGB LED chains,
+    // it is necessary to synchronize, so it is necessary to communicate RGB information.
+    // In that case, define the RGBLIGHT_SPLIT macro.
+    //
+    // Otherwise, if the master side MCU drives both sides RGB LED chains,
+    // there is no need to communicate.
+#endif
+} Serial_m2s_buffer_t;
+
+extern volatile Serial_m2s_buffer_t serial_m2s_buffer;
+
+void serial_master_init(void);
+void serial_slave_init(void);
+
+#endif