soc/mediatek/mt8188: Add a stub implementation of the MT8188 SoC

Add new folder and basic drivers for Mediatek SoC 'MT8188'.

Difference of modules including in this patch between MT8188 and
existing SoCs:
Timer:
	Similar to MT8195 and MT8186, MT8188 uses v2 timer.
EMI/PLL/SPI:
	Different from existing SoCs.

The implementation is based on these files:
MT8188G_Application Processor Technical Brief_v0.4.pdf
MT8188G_Functional Specification v0.4.pdf
MT8188 Application Processor Registers-1.pdf
MT8188 Application Processor Registers-2.pdf

TEST=saw the coreboot uart log to bootblock
BUG=b:233720142

Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Change-Id: I3320f3d49a9b9ed781ceb812e4341e379db4ac20
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65585
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yidi Lin <yidilin@chromium.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/soc/mediatek/mt8188/emi.c b/src/soc/mediatek/mt8188/emi.c
new file mode 100644
index 0000000000..bb503bb6ca
--- /dev/null
+++ b/src/soc/mediatek/mt8188/emi.c
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/*
+ * This file is created based on MT8188 Functional Specification
+ * Chapter number: 3.7
+ */
+
+#include <soc/emi.h>
+
+size_t sdram_size(void)
+{
+	return (size_t)4 * GiB;
+}