drm/mediatek: mtk_hdmi: Split driver and add common probe function

In preparation for adding a new driver for the HDMI TX v2 IP,
split out the functions that will be common between the already
present mtk_hdmi (v1) driver and the new one.

Since the probe flow for both drivers is 90% similar, add a common
probe function that will be called from each driver's .probe()
callback, avoiding lots of code duplication.

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20251023-mediatek-drm-hdmi-v2-v11-4-7873ec4a1edf@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: AngeloGioacchino Del Regno

drivers/gpu/drm/mediatek/Kconfig

@@ -30,9 +30,18 @@ config DRM_MEDIATEK_DP
 	help
 	  DRM/KMS Display Port driver for MediaTek SoCs.
 
+config DRM_MEDIATEK_HDMI_COMMON
+	tristate
+	depends on DRM_MEDIATEK
+	select DRM_DISPLAY_HDMI_HELPER
+	select DRM_DISPLAY_HELPER
+	select SND_SOC_HDMI_CODEC if SND_SOC
+	help
+	  MediaTek SoC HDMI common library
+
 config DRM_MEDIATEK_HDMI
 	tristate "DRM HDMI Support for Mediatek SoCs"
 	depends on DRM_MEDIATEK
-	select SND_SOC_HDMI_CODEC if SND_SOC
+	select DRM_MEDIATEK_HDMI_COMMON
 	help
 	  DRM/KMS HDMI driver for Mediatek SoCs

drivers/gpu/drm/mediatek/Makefile

@@ -21,6 +21,7 @@ mediatek-drm-y := mtk_crtc.o \
 
 obj-$(CONFIG_DRM_MEDIATEK) += mediatek-drm.o
 
+obj-$(CONFIG_DRM_MEDIATEK_HDMI_COMMON) += mtk_hdmi_common.o
 obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_cec.o
 obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_hdmi.o
 obj-$(CONFIG_DRM_MEDIATEK_HDMI) += mtk_hdmi_ddc.o