arc: Add support for HS Development Kit board

ARC HS Development Kit board is a new low-cost
development platform sporting ARC HS38 in real silicon
with nice set of features such as:
 * Quad-core ARC HS38 with 512 kB L2 cache and running @1GHz
 * 4Gb of DDR (we use only lowest 1Gb out of it now)
 * Lots of DesigWare peripherals
 * Different connectivity modules:
     - Synopsys HAPS HT3
     - Arduino-compatible connector
     - MikroBUS

This initial commit supports the following peripherals:
 * UART (DW 8250)
 * Ethernet (DW GMAC)
 * SD/MMC (DW Mobile Storage)
 * USB 1.1 & 2.0

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/configs/hsdk_defconfig b/configs/hsdk_defconfig
new file mode 100644
index 0000000..0018c04
--- /dev/null
+++ b/configs/hsdk_defconfig
@@ -0,0 +1,37 @@
+CONFIG_ARC=y
+CONFIG_ISA_ARCV2=y
+CONFIG_TARGET_HSDK=y
+CONFIG_SYS_TEXT_BASE=0x81000000
+CONFIG_SYS_CLK_FREQ=1000000000
+CONFIG_DEFAULT_DEVICE_TREE="hsdk"
+CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SYS_PROMPT="hsdk# "
+# CONFIG_CMD_IMLS is not set
+# CONFIG_CMD_FLASH is not set
+CONFIG_CMD_MMC=y
+CONFIG_CMD_USB=y
+# CONFIG_CMD_SETEXPR is not set
+CONFIG_CMD_DHCP=y
+CONFIG_CMD_PING=y
+CONFIG_CMD_EXT2=y
+CONFIG_CMD_EXT4=y
+CONFIG_CMD_EXT4_WRITE=y
+CONFIG_CMD_FAT=y
+CONFIG_OF_CONTROL=y
+CONFIG_OF_EMBED=y
+CONFIG_NET_RANDOM_ETHADDR=y
+CONFIG_DM=y
+CONFIG_MMC=y
+CONFIG_MMC_DW=y
+CONFIG_DM_ETH=y
+CONFIG_ETH_DESIGNWARE=y
+CONFIG_DM_SERIAL=y
+CONFIG_SYS_NS16550=y
+CONFIG_USB=y
+CONFIG_DM_USB=y
+CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_EHCI_GENERIC=y
+CONFIG_USB_OHCI_HCD=y
+CONFIG_USB_OHCI_GENERIC=y
+CONFIG_USB_STORAGE=y
+CONFIG_USE_PRIVATE_LIBGCC=y