drivers: video: formats: add grayscale formats

Add the grayscale formats in the same packing as defined by MIPI.
The Linux V4L2 naming is preserved.

Signed-off-by: Josuah Demangeon <me@josuah.net>

Author: josuah

include/zephyr/drivers/video.h

@@ -1009,6 +1009,59 @@ void video_closest_frmival(const struct device *dev, enum video_endpoint_id ep,
  */
 #define VIDEO_PIX_FMT_SRGGB14P VIDEO_FOURCC('p', 'R', 'E', 'E')
 
+/**
+ * @}
+ */
+
+/**
+ * @name Grayscale formats
+ * Luminance (Y) channel only, in various bit depth and packing.
+ *
+ * When the format includes more than 8-bit per pixel, a strategy becomes needed to pack
+ * the bits over multiple bytes, as illustrated for each format.
+ *
+ * The number above the 'Y', 'y' are hints about which pixel number the following bits belong to.
+ *
+ * @{
+ */
+
+/**
+ * Same as Y8 (8-bit luma-only) following the standard FOURCC naming,
+ * or L8 in some graphics libraries.
+ *
+ * @code{.unparsed}
+ *   0          1          2          3
+ * | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | ...
+ * @endcode
+ */
+#define VIDEO_PIX_FMT_GREY VIDEO_FOURCC('G', 'R', 'E', 'Y')
+
+/**
+ * @code{.unparsed}
+ *   0          1          2          3          3 2 1 0
+ * | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | yyyyyyyy | ...
+ * @endcode
+ */
+#define VIDEO_PIX_FMT_Y10P VIDEO_FOURCC('Y', '1', '0', 'P')
+
+/**
+ * @code{.unparsed}
+ *   0          1          1   0      2          3          3   2
+ * | Yyyyyyyy | Yyyyyyyy | yyyyyyyy | Yyyyyyyy | Yyyyyyyy | yyyyyyyy | ...
+ * | Yyyyyyyy | Yyyyyyyy | yyyyyyyy | Yyyyyyyy | Yyyyyyyy | yyyyyyyy | ...
+ * @endcode
+ */
+#define VIDEO_PIX_FMT_Y12P VIDEO_FOURCC('Y', '1', '2', 'P')
+
+/**
+ * @code{.unparsed}
+ *   0          1          2          3          1 0      2   1    3     2
+ * | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | yyyyyyyy yyyyyyyy yyyyyyyy | ...
+ * | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | Yyyyyyyy | yyyyyyyy yyyyyyyy yyyyyyyy | ...
+ * @endcode
+ */
+#define VIDEO_PIX_FMT_Y14P VIDEO_FOURCC('Y', '1', '4', 'P')
+
 /**
  * @}
  */
@@ -1112,6 +1165,7 @@ static inline unsigned int video_bits_per_pixel(uint32_t pixfmt)
 	case VIDEO_PIX_FMT_GBRG8:
 	case VIDEO_PIX_FMT_GRBG8:
 	case VIDEO_PIX_FMT_RGGB8:
+	case VIDEO_PIX_FMT_GREY:
 		return 8;
 	case VIDEO_PIX_FMT_SBGGR10P:
 	case VIDEO_PIX_FMT_SGBRG10P: