arm: mach-k3: Add basic support for AM642 SoC definition

The AM642 SoC belongs to the K3 Multicore SoC architecture platform,
providing advanced system integration to enable applications such as
Motor Drives, PLC, Remote IO and IoT Gateways.

Some highlights of this SoC are:
* Dual Cortex-A53s in a single cluster, two clusters of dual Cortex-R5F
  MCUs, and a single Cortex-M4F.
* Two Gigabit Industrial Communication Subsystems (ICSSG).
* Integrated Ethernet switch supporting up to a total of two external
  ports.
* PCIe-GEN2x1L, USB3/USB2, 2xCAN-FD, eMMC and SD, UFS, OSPI memory
  controller, QSPI, I2C, eCAP/eQEP, ePWM, ADC, among other
  peripherals.
* Centralized System Controller for Security, Power, and Resource
  Management (DMSC).

See AM64X Technical Reference Manual (SPRUIM2, Nov 2020)
for further details: https://www.ti.com/lit/pdf/spruim2

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
diff --git a/arch/arm/mach-k3/Kconfig b/arch/arm/mach-k3/Kconfig
index c7d1861..35edc6d 100644
--- a/arch/arm/mach-k3/Kconfig
+++ b/arch/arm/mach-k3/Kconfig
@@ -10,6 +10,9 @@
 config SOC_K3_J721E
 	bool "TI's K3 based J721E SoC Family Support"
 
+config SOC_K3_AM642
+	bool "TI's K3 based AM642 SoC Family Support"
+
 endchoice
 
 config SYS_SOC
@@ -19,16 +22,18 @@
 	hex
 	default 0x80000 if SOC_K3_AM6
 	default 0x100000 if SOC_K3_J721E
+	default 0x1c0000 if SOC_K3_AM642
 	help
-	  Describes the total size of the MCU MSRAM. This doesn't
-	  specify the total size of SPL as ROM can use some part
-	  of this RAM. Once ROM gives control to SPL then this
-	  complete size can be usable.
+	  Describes the total size of the MCU or OCMC MSRAM present on
+	  the SoC in use. This doesn't specify the total size of SPL as
+	  ROM can use some part of this RAM. Once ROM gives control to
+	  SPL then this complete size can be usable.
 
 config SYS_K3_MAX_DOWNLODABLE_IMAGE_SIZE
 	hex
 	default 0x58000 if SOC_K3_AM6
 	default 0xc0000 if SOC_K3_J721E
+	default 0x180000 if SOC_K3_AM642
 	help
 	  Describes the maximum size of the image that ROM can download
 	  from any boot media.
@@ -51,6 +56,7 @@
 	hex
 	default 0x41c7fbfc if SOC_K3_AM6
 	default 0x41cffbfc if SOC_K3_J721E
+	default 0x701bebfc if SOC_K3_AM642
 	help
 	  Address at which ROM stores the value which determines if SPL
 	  is booted up by primary boot media or secondary boot media.