document HDF5

Author: perazz

pages/spec/metapackages.md

@@ -102,3 +102,19 @@ Currently verified system configurations are:
 MPI C++ support on macOS is missing because homebrew is built with `clang`, whose C++ ABI is incompatible with the GNU C++ ABI needed to link against gfortran.
 :::
 
+## HDF5
+
+```{code-block} toml
+:emphasize-lines: 2
+name = "my_science_app"
+dependencies.hdf5 = "*"
+```
+
+HDF5 is supported for Fortran, C and C++ languages. The `pkg-config` backend is employed by `fpm` to find a valid local HDF5 installation, so, please insure that `pkg-config` is also available when using this metapackage. 
+
+Both the default and the high-level (`HL`) interfaces are linked against if available. 
+On Ubuntu, special steps are taken on Ubuntu to ensure `HL` are added. On Ubuntu with oneAPI compilers, CMake HDF5 installations are supported (`apt` versions only support `gfortran`).
+
+:::{note}
+Codes using HDF5 built with `oneAPI` compilers should not have the `-standard-semantics` flag: it changes module name mangling from `_mp_` to `_MP_` which makes HDF5 modules unavailable.
+:::