Documentation for ARC port

(a) ABI doc:
    https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/wiki/files/ARCv2_ABI.pdf

(b) Programmer's Reference Manual (PRM) : needs a download request to be filled
    https://www.synopsys.com/dw/ipdir.php?ds=arc-hs44-hs46-hs48
    https://www.synopsys.com/dw/doc.php/ds/cc/programmers-reference-manual-ARC-HS.pdf

As of port merge (and Florian's patch to fix static TLS), glibc testsuite
(cross-test setup) has following failures:

FAIL: elf/tst-audit14
FAIL: elf/tst-audit15
FAIL: elf/tst-audit16
FAIL: elf/tst-ldconfig-ld_so_conf-update
FAIL: elf/tst-libc_dlvsym
FAIL: elf/tst-libc_dlvsym-static
FAIL: iconv/test-iconvconfig		# Needs gconv installed
FAIL: io/ftwtest			# Requires execution by non-root
FAIL: io/tst-lockf
FAIL: libio/tst-wfile-sync
FAIL: locale/tst-localedef-path-norm
FAIL: nptl/test-cond-printers		# needs Python3 and target GDB on target
FAIL: nptl/test-condattr-printers	#    ditto
FAIL: nptl/test-mutex-printers		#    ditto
FAIL: nptl/test-mutexattr-printers	#    ditto
FAIL: nptl/test-rwlock-printers		#    ditto
FAIL: nptl/test-rwlockattr-printers	#    ditto
FAIL: nptl/tst-umask1			# passes if run natively on target (NFS ACLv3 support needed)
FAIL: nss/bug-erange
FAIL: nss/tst-nss-files-hosts-getent
FAIL: nss/tst-nss-files-hosts-multi
FAIL: posix/bug-ga2
FAIL: posix/globtest			# require same user on target and host
FAIL: posix/tst-getaddrinfo5
FAIL: stdio-common/tst-vfprintf-width-prec
FAIL: stdio-common/tst-vfprintf-width-prec-alloc
FAIL: stdio-common/tst-vfprintf-width-prec-mem
FAIL: string/tst-strerror
FAIL: string/tst-strsignal
FAIL: sunrpc/bug20790			# missing cpp on target
FAIL: timezone/tst-tzset

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

NEWS

@@ -15,6 +15,17 @@ Major new features:
 
 * New locale added: ckb_IQ (Kurdish/Sorani spoken in Iraq)
 
+* Support for Synopsys ARC HS cores (ARCv2 ISA) running Linux has been
+  added. This port requires at least binutils-2.32, gcc-8.3 and Linux-5.1.
+  Three ABIs are supported:
+
+     - arc-linux-gnu
+     - arc-linux-gnuhf
+     - arceb-linux-gnu
+
+  The arc* ABI is little-endian while arceb is big-endian. All ABIs use
+  64-bit time (y2038 safe) and 64-bit file offsets (LFS default).
+
 * The GNU C Library now loads audit modules listed in the DT_AUDIT and
   DT_DEPAUDIT dynamic section entries of the main executable.
 

README

@@ -24,6 +24,7 @@ The GNU C Library supports these configurations for using Linux kernels:
 
 	aarch64*-*-linux-gnu
 	alpha*-*-linux-gnu
+	arc*-*-linux-gnu
 	arm-*-linux-gnueabi
 	csky-*-linux-gnuabiv2
 	hppa-*-linux-gnu

manual/install.texi

@@ -512,6 +512,8 @@ Library with support for IEEE long double.
 @c powerpc64le performs an autoconf test to verify the compiler compiles with
 @c commands like "$CC -c foo.c -mabi=ibmlongdouble -mlong-double-128".
 
+For ARC architecture builds, GCC 8.3 or higher is needed.
+
 For multi-arch support it is recommended to use a GCC which has been built with
 support for GNU indirect functions.  This ensures that correct debugging
 information is generated for functions selected by IFUNC resolvers.  This
@@ -537,6 +539,8 @@ For PowerPC 64-bits little-endian (powerpc64le), @command{objcopy} is required
 to support @option{--update-section}.  This option requires binutils 2.26 or
 newer.
 
+ARC architecture needs @code{binutils} 2.32 or higher for TLS related fixes.
+
 @item
 GNU @code{texinfo} 4.7 or later