ALL stakeholders need mapping and priortising. Creating and regularly updateing a stakeholder matrix is a useful
exercise, especially the updating as definitions and priorities are fluid.
Each group will have different requirements and you'll need to manage available resources in relation to your priority map.
Each group will also require dialogue with appropriate tone, language and channels familiar to them. Don't expect all groups to respond effectively to how you want to communicate. There has to be informal negotiation.
Listening is key to all stakeholder engagement.

A stakeholder matrix is part of overall management. The best systems are similar to an organization's risk or enterprise management management system, probably based on the Deming cycle. See the model described in the Mass Transit Railway Corporation's Sustainability Reports in 2012 and earlier https://www.mtr.com.hk/en/corporate/sustainability/sustainability_reporting.html. What is needed is a system to make the engagement process transparent to top management and stakeholders for the allocation of resources and ownership, and remuneration of short and long term pay incentives for achieving engagement goals.

It will depend on how you define stakeholders. If for example employes get shares over
time they become stakeholders, and there could be many. Different type of shares (e. g., preferred shares) may be issued to investors. Each company will have the process of issuing shares clearly documented.

Since the late 1990's stakeholder engagement has taken a significant leap with the growing awarenss an application of Integral Psychology. The appreciation that the differing wordviews of different stakeholders requires differing methods. This tratified approach offers great innovation and not least the avoidance of workdview myopia which may for example lead to unhealthy excess. So the saying 'different strokes for different folks' has taken on a whole new meaning and reliability as the science catches up with folklore. In my experience such awareness lifts the practice innovation into what I call 'Factor 100 Innovation' - an exponential increase in human creativity, resilience and the quality of management / stakeholder decisions.

In my experiance (integral product development), stakeholders are explored by mapping the system you'll design in the greater context. Thinking troughout the life cycle, the critical stakeholders come in the picture.
Patrik

That question has 3 parts - stakeholder identification, analysis & prioritisation and engagement.
1) The stakeholder identification exercise needs to be thorough. There are always more people affected by a project than you first think. James Brown's text, "The Handbook of Program Management", provides good guidance. Some hints below:
1.1 Follow the money! Whoever is paying is a stakeholder. Also, if the program produces savings or additional costs for an organization then the organization is also a stakeholder.
1.2 Follow the resources. Every entity (division, managers etc.)that provides resources are stakeholders.
1.3 Follow the deliverables. Whoever is the recipient of the product or service the program is providing is a stakeholder.
1.4 Follow the signatures. The individual who signs off on completion of the final product or service (or phases thereof) is a stakeholder. Note: This may or may not be the recipient referred to in the previous bullet. Often there may be more recipients than signatories.
1.5 Ask team members, customers, and any other confirmed stakeholder to help you identify additional stakeholders.
books
1.6 Look for the "Unofficial People of Influence." These may be people who are trusted by high-level leaders or who wield a lot of power through influence and not position.

1. One useful way to do PRIORITISATION to ensure YOU are making good use of your time is to demarcate the various stakeholders into the following 4 groups. Bear in mind that one will have to review this demarcation from time to time to see if changed circumstances will warrant any set of stakeholders to be moved to a different bucket. The four buckets in decreasing order of importance in terms of attention to be paid are:
2. High power high interest - Always at No.1 [manage this group closely, give them updated status reports, get their inputs etc]
3. High power low interest - Can be No 2 or No 3
4. Low power high interest - Can be No.2 or No. 3
5. Low power low interest - Always No. 4
6. And yes, you cannot cater to and serve all stakeholders equally. That is neither necessary nor productive. Tailor the depth and breadth of engagement for different category of stakeholders.

We have to keep iterating the 4 stage cycle of identify, analyse, prioritise and engage.

That question has 3 parts - stakeholder identification, analysis & prioritisation and engagement.
1) The stakeholder identification exercise needs to be thorough. There are always more people affected by a project than you first think. James Brown's text, "The Handbook of Program Management", provides good guidance. Some hints below:
1.1 Follow the money! Whoever is paying is a stakeholder. Also, if the program produces savings or additional costs for an organization then the organization is also a stakeholder.
1.2 Follow the resources. Every entity (division, managers etc.)that provides resources are stakeholders.
1.3 Follow the deliverables. Whoever is the recipient of the product or service the program is providing is a stakeholder.
1.4 Follow the signatures. The individual who signs off on completion of the final product or service (or phases thereof) is a stakeholder. Note: This may or may not be the recipient referred to in the previous bullet. Often there may be more recipients than signatories.
1.5 Ask team members, customers, and any other confirmed stakeholder to help you identify additional stakeholders.
books
1.6 Look for the "Unofficial People of Influence." These may be people who are trusted by high-level leaders or who wield a lot of power through influence and not position.

1. One useful way to do PRIORITISATION to ensure YOU are making good use of your time is to demarcate the various stakeholders into the following 4 groups. Bear in mind that one will have to review this demarcation from time to time to see if changed circumstances will warrant any set of stakeholders to be moved to a different bucket. The four buckets in decreasing order of importance in terms of attention to be paid are:
2. High power high interest - Always at No.1 [manage this group closely, give them updated status reports, get their inputs etc]
3. High power low interest - Can be No 2 or No 3
4. Low power high interest - Can be No.2 or No. 3
5. Low power low interest - Always No. 4
6. And yes, you cannot cater to and serve all stakeholders equally. That is neither necessary nor productive. Tailor the depth and breadth of engagement for different category of stakeholders.

We have to keep iterating the 4 stage cycle of identify, analyse, prioritise and engage.