feat(oran_fhlib_5g): Documentation for Arm targets

doc/ORAN_FHI7.2_Tutorial.md

@@ -403,7 +403,8 @@ git apply ~/openairinterface5g/cmake_targets/tools/oran_fhi_integration_patches/
 Compile the fronthaul interface library by calling `make` and the option
 `XRAN_LIB_SO=1` to have it build a shared object. Note that we provide two
 environment variables `RTE_SDK` for the path to the source tree of DPDK, and
-`XRAN_DIR` to set the path to the fronthaul library.
+`XRAN_DIR` to set the path to the fronthaul library.  
+For building for a Arm target, set as well the environment variable `TARGET=armv8`.
 
 **Note**: you need at least gcc-11 and g++-11.
 
@@ -420,6 +421,28 @@ WIRELESS_SDK_TOOLCHAIN=gcc RTE_SDK=~/dpdk-stable-20.11.9/ XRAN_DIR=~/phy/fhi_lib
 The shared library object `~/phy/fhi_lib/lib/build/libxran.so` must be present
 before proceeding.
 
+## For Arm targets only: Install the Arm RAN Acceleration library
+
+Clone, configure and build ArmRAL:
+
+Note: Use option `-DCMAKE_INSTALL_PREFIX=<install-dir>` of cmake to set the installation directory of ArmRAL to `<install-dir>`.
+If you omit this option, ArmRAL is installed into `/usr/local`.
+
+```
+git clone https://git.gitlab.arm.com/networking/ral.git ~/ral
+cd ~/ral
+git checkout armral-25.01
+mkdir build
+cd build
+cmake -GNinja -DBUILD_SHARED_LIBS=On ../
+ninja
+```
+
+Once ArmRAL is configured at your convenience and built, you can install it:
+```
+ninja install
+```
+
 ## Build OAI gNB
 
 You can now proceed building OAI. You build it the same way as for other